Teacup

A community-driven DSL for creating user interfaces on iOS and OS X.

Using Teacup, you can create and style layouts and keeping your code dry. The goal is to offer a rubyesque (well, actually a rubymotion-esque) way to create interfaces programmatically.

A note about Teacup and MotionKit

Read a letter from Colin T.A. Gray regarding the future of Teacup and introducing MotionKit, its successor.

Check out some sample apps!

• iOS
  • Hai
  • AutoLayout
  • Sweettea Example
• OS X
  • Tweets - ported from RubyMotionSamples
  • simple

Quick Install

> gem install teacup

and in your Rakefile

require 'teacup'

10 second primer, iOS

1. Create a UIViewController subclass:

   class MyController < UIViewController

2. Assign a stylesheet name:

   class MyController < UIViewController
     stylesheet :main_screen

3. Create a layout:

   class MyController < UIViewController
     stylesheet :main_screen
   
     def teacup_layout
       subview(UIButton, :hi_button)
     end
   end

4. Create the stylesheet (in app/styles/ or somewhere near the controller)

   Teacup::Stylesheet.new :main_screen do
     style :hi_button,
       origin: [10, 10],
       title: 'Hi!'
   end

10 second primer, OS X

Pretty much the same! Note that on OS X, view coordinates are based on having the origin in the bottom-left corner, not the upper-left like it is on every other GUI system ever. :-|

You should use the TeacupWindowController parent class instead of NSWindowController

1. Create a TeacupWindowController subclass.

   class MyController < TeacupWindowController

2. Assign a stylesheet name:

   class MyController < TeacupWindowController
     stylesheet :main_window

3. Create a layout:

   class MyController < TeacupWindowController
     stylesheet :main_window
   
     def teacup_layout
       subview(NSButton, :hi_button)
     end
   end

4. Create the stylesheet (in app/styles/ or somewhere near the controller)

   Teacup::Stylesheet.new :main_window do
     style :hi_button,
       origin: [10, 10],
       title: 'Hi!'
   end

Teacup

Teacup's goal is to facilitate the creation and styling of your view hierarchy. Say "Goodbye!" to Xcode & XIB files!

Teacup is composed of two systems:

• Layouts A DSL to create Views and to organize them in a hierarchy. You assign the style name and style classes from these methods.

• Stylesheets Store the "styles" that get applied to your views. The stylesheet DSL is meant to resemble CSS, but is targeted at iOS, and so the precedence rules are very different.

Teacup supports Pixate and NUI, too, so you can use those systems for styling and Teacup to manage your view hierarchy and apply auto-layout constraints. Teacup can also integrate with the motion-layout gem!

Changes in 3.0

There is one significant change in version 3.0. In every version of Teacup prior (from 0.2.0 to 2.3.0) the controller layout was usually created by calling a class method called layout. It was discovered, embarrassingly late, that this system is causing memory leaks. To fix it we had to remove this feature altogether. So if you are looking at old Teacup examples, you will see this block syntax that is no longer offered. It is easy to update to 3.0, though:

# <= 2.3.0
class MyController < UIViewController
  layout(:root_stylename) do  # <= this block is what caused the memory leak!
    # teacup code goes here
  end
end

# 3.0
class MyController < UIViewController
  def teacup_layout  # in 3.0 we just changed it to be a method
    # introduced in 3.0, this is how you assign a stylename to the root view
    root(:root_stylename, { background: UIColor.blueColor })
    # teacup code goes here - no other code changes necessary
  end
  # actually, this method still works as long as you don't pass a block.  It's
  # the same as calling `root(stylename, {})`
  layout(:root_stylename, {})
end

Table of Contents

• Layouts — define your views
• Stylesheets — style your views
  • Using and re-using styles in a Stylesheet
  • Style via Stylename
  • Extending Styles
  • Style via View Class
  • Importing stylesheets
  • Style via UIAppearance (iOS only)
• UITableViews - This is important if you are using styles and constraints in a UITableViewDelegate.
• More Teacup features
  • Styling View Properties
  • Orientation Styles (iOS only)
  • Animation additions
  • Style Handlers
  • Frame Calculations
  • Auto-Layout
  • Motion-Layout
  • Stylesheet extensions
    • Autoresizing Masks
    • Device detection (iOS only)
    • Rotation helpers (iOS only)
• Showdown — Cocoa vs Teacup
• The Nitty Gritty — some implementation details and gotchas
• Advanced Teacup Tricks
  • Including Teacup::Layout on arbitrary classes
  • Sweettea
• Misc notes
• The Dummy — fixes “uncompiled selector” errors

Layouts

The Teacup::Layout module is mixed into UIViewController and UIView on iOS, and NSWindowController, NSViewController, and NSView on OS X. These classes can take advantage of the view-hierarchy DSL.

You saw an example in the primer, using the UIViewController/NSWindowController class method layout and the teacup_layout method. You could just as easily use Teacup's DSL to create your views from a loadView method, for instance you might want to use a custom view subclass as your root view. An example might look like this:

# controller example
class MyController < UIViewController

  def loadView
    # we will create the controller's view, assigning it the stylename :root
    self.view = layout(FancyView, :root) do
      # these subviews will be added to `self.view`
      subview(UIToolbar, :toolbar)
      subview(UIButton, :hi_button)
    end
  end

end

You can use very similar code in your view subclasses.

# view example
#
# if you use Teacup in all your projects, you can bundle your custom views with
# their own stylesheets
def MyView < UIView

  def initWithFrame(frame)
    super.tap do
      self.stylesheet = :my_stylesheet
      subview(UIImageView, :image)
    end
  end

end

The layout and subview methods are the work horses of the Teacup view DSL.

• layout(view|ViewClass, stylename, style_classes, additional_styles, &block)
  • view|ViewClass - You can layout an existing class or you can have Teacup create it for you (it just calls new on the class, nothing special). This argument is required.
  • stylename (Symbol) - This is the name of a style in your stylesheet. It is optional
  • style_classes ([Symbol,...]) - Other stylenames, they have lower priority than the stylename.
  • additional_styles (Hash) - You can pass other styles in here as well, either to override or augment the settings from the Stylesheet. It is common to use this feature to assign the delegate or dataSource.
  • &block - See discussion below
  • Returns the view that was created or passed to layout.
  • only the view arg is required. You can pass any combination of stylename, style_classes, and additional_styles (some, none, or all).
• subview(view|UIViewClass, stylename, style_classes, additional_styles, &block)
  • Identical to layout, but adds the view to the current target

The reason it is so easy to define view hierarchies in Teacup is because the layout and subview methods can be "nested" by passing a block.

subview(UIView, :container) do  # create a UIView instance and give it the stylename :container
  subview(UIView, :inputs) do  # create another container
    # these views will be added to the :inputs view
    @email_input = subview(UITextField, :email_input)
    @password_input = subview(UITextField, :password_input)
  end
  # this view will be added to :container
  subview(UIButton.buttonWithType(UIButtonTypeRoundedRect), :submit_button)
end

These methods are defined in the Layout module. And guess what!? It's easy to add your own view helpers! I refer to this as a "partials" system, but really it's just Ruby code (and isn't that the best system?).

# the methods you add here will be available in UIView/NSView,
# UIViewController/NSViewController/NSWindowController, and any of your own
# classes that `include Teacup::Layout`
module Teacup::Layout

  # creates a button and assigns a default stylename
  def button(*args, &block)
    # apply a default stylename
    args = [:button] if args.empty?

    # instantiate a button and give it a style class
    subview(UIButton.buttonWithType(UIButtonTypeCustom), *args, &block)
  end

  # creates a button with an icon image and label
  def button_with_icon(icon, title)
    label = UILabel.new
    label.text = title
    label.sizeToFit

    image_view = UIImageView.new
    image_view.image = icon
    image_view.sizeToFit

    button = UIButton.buttonWithType(UIButtonTypeCustom)
    button.addSubview(image_view)
    button.addSubview(label)

    # code could go here to position the icon and label, or at could be handled
    # by the stylesheet

    subview(button)
  end

end

example use of the helper methods

class MyController < UIViewController

  def teacup_layout
    @button1 = button()
    @button2 = button(:blue_button)
    @button3 = button_with_icon(UIImage.imageNamed('email_icon'), 'Email')
  end

end

The Controller#teacup_layout method is going to be the first or second thing you add to a controller when you are building an app with Teacup. Inside you will add subviews using subview or you can create a view using the layout method (subview delegates most of its work to layout)

After the views have been added and styles have been applied Teacup calls the layoutDidLoad method. If you need to perform some additional initialization on your views, you can do it in this method.

Stylesheets

This is where you will store your styling-related code. Migrating code from your controller or custom view into a stylesheet is very straightforward. The method names map 1::1.

# classic Cocoa/UIKit
def viewDidLoad
  self.view.backgroundColor = UIColor.grayColor
  #         ^.............^
end

# in Teacup
def viewDidLoad
  self.stylesheet = :main
  self.view.stylename = :root
end

Teacup::Stylesheet.new :main do
  style :root,
    backgroundColor: UIColor.grayColor
#   ^.............^
end

Nice! We turned three lines of code into nine! Well, obviously the benefits come in when we have lots of style code, and when you need to do app-wide styling.

You can store stylesheets in any file. It is common to use app/styles.rb or app/styles/main.rb, if you have more than a few of 'em. The Teacup::Stylesheet constructor accepts a stylesheet name and a block, which will contain your style declarations.

Teacup::Stylesheet.new :main_menu do
  style :ready_to_play_button,
    backgroundColor: UIColor.blackColor,
    frame: [[20, 300], [50, 20]]
end

Teacup::Stylesheet[:main_menu]  # returns this stylesheet

Any method that accepts a single value can be assigned in a stylesheet. Please don't abuse this by hiding application logic in your stylesheets - these are meant for design, not behavior.

Limelight syntax

If you want to use a shorter syntax, you can use the "Limelight" inspired syntax:

Teacup::Stylesheet.new :main_menu do
  ready_to_play_button do
    backgroundColor UIColor.blackColor
    frame [[20, 300], [50, 20]]
  end
end

This creates the same style hashes as style :ready_to_play_button, so you have access to all the features that are available in the "traditional" syntax.

Using and re-using styles in a Stylesheet

• Styles are be applied via stylename (style :label) or class (style UILabel)
• Styles can extend other styles (style :big_button, extends: :button)
• A stylesheet can import other stylesheets (import :app)
• The special Appearance stylesheet can be used to apply styles to UIAppearance (Teacup::Appearance.new)

Let's look at each in turn.

Style via Stylename

This is the most common way to apply a style.

class MainController < UIViewController

  stylesheet :main  # <= assigns the stylesheet named :main to this controller

  def teacup_layout
    subview(UILabel, :h1)  # <= :h1 is the stylename
  end

end

Teacup::Stylesheet.new :main do  # <= stylesheet name

  style :h1,  # <= style name
    font: UIFont.systemFontOfSize(20)  # <= and this style is applied

end

When the stylesheet is applied (at the end of the layout block, when all the views have been added), its font property will be assigned the value UIFont.systemFontOfSize(20).

But we didn't assign any text!

We can tackle this a couple ways. You can apply "last-minute" styles in the layout and subview methods:

def teacup_layout
  subview(UILabel, :h1,
    # the `subview` and `layout` methods can apply styles
    text: "Omg, it's full of stars"
    )
end

In this case though we just have static text, so you can assign the text using the stylesheet:

Teacup::Stylesheet.new :main do

  style :h1,
    font: UIFont.systemFontOfSize(20)

  style :main_header,
    text: "Omg, it's full of stars",
    font: UIFont.systemFontOfSize(20)

end

Extending Styles

Not very DRY though is it!? We have to use a new style (:main_header) because not all our labels say "OMG", but we want to use our font from the :h1 style. We can tell the :main_header style that it extends the :h1 style:

def teacup_layout
  subview(UILabel, :main_header)
end

Teacup::Stylesheet.new :main do

  style :h1,
    font: UIFont.systemFontOfSize(20)

  style :main_header, extends: :h1,
    text: "Omg, it's full of stars"

end

A common style when writing stylesheets is to use variables to store settings you want to re-use.

Teacup::Stylesheet.new :main do
  h1_font = UIFont.systemFontOfSize(20)

  style :h1,
    font: h1_font
  style :main_header, extends: :h1,
    text: "Omg, it's full of stars"
end

And you're not limited to one class that you can extend, it accepts an array

Teacup::Stylesheet.new :main do
  h1_font = UIFont.systemFontOfSize(20)

  style :h1,
    font: h1_font

  style :label,
    textColor: UIColor.black

  style :main_header, extends: [:h1, :label],
    text: "Omg, it's full of stars"
end

Style via View Class

If you need to apply styles to all instances of a UIView/NSView subclass, you can do so by applying styles to a class name instead of a symbol. This feature is handy at times when you might otherwise use UIAppearance (which teacup also supports!).

Teacup::Stylesheet.new :app do

  style UILabel,
    font: UIFont.systemFontOfSize(20)

  style UITableView,
    backgroundColor: UIColor.blackColor

end

Importing stylesheets

We've touched on the ability to write styles, extend styles, and apply styles to a class. Now we can introduce another feature that is even more useful for applying styles to your entire app: import a stylesheet.

When you import a stylesheet, you receive all of its styles and you gain access to its instance variables. This way you can define colors and margins and such in a "parent" stylesheet.

Teacup::Stylesheet.new :app do

  @header_color = UIColor.colorWithRed(7/255.0, green:16/255.0, blue:95/255.0, alpha: 1)
  @background_color = UIColor.colorWithRed(216/255.0, green:226/255.0, blue:189/255.0, alpha: 1)

  style :root,
    backgroundColor: @background_color

  style :header,
    textColor: @header_color

end

Teacup::Stylesheet.new :main do
  import :app

  style :subheader, extends: :header  # <= the :header style is imported from the :app stylesheet

  style :button,
    titleColor: @header_color  # <= @header_color is imported, too
end

Style via UIAppearance

iOS only

And lastly, the UIAppearance protocol is supported by creating an instance of Teacup::Appearance. There is debatable benefit to using UIAppearance, because it will apply styles to views that are outside your control, like the camera/image pickers and email/message controllers.

But, it does come in handy sometimes... so here it is!

Teacup::Appearance.new do

  # UINavigationBar.appearance.setBarTintColor(UIColor.blackColor)
  style UINavigationBar,
    barTintColor: UIColor.blackColor,
    titleTextAttributes: {
      UITextAttributeFont => UIFont.fontWithName('Trebuchet MS', size:24),
      UITextAttributeTextShadowColor => UIColor.colorWithWhite(0.0, alpha:0.4),
      UITextAttributeTextColor => UIColor.whiteColor
    }

  # UINavigationBar.appearanceWhenContainedIn(UINavigationBar, nil).setColor(UIColor.blackColor)
  style UIBarButtonItem, when_contained_in: UINavigationBar,
    tintColor: UIColor.blackColor

  # UINavigationBar.appearanceWhenContainedIn(UIToolbar, UIPopoverController, nil).setColor(UIColor.blackColor)
  style UIBarButtonItem, when_contained_in: [UIToolbar, UIPopoverController],
    tintColor: UIColor.blackColor

end

In your AppDelegate you need to call Teacup::Appearance.apply. It will get called automatically using the UIApplicationDidFinishLaunchingNotification, but that notification is triggered after the method AppDelegate#didFinishLaunching(withOptions:) is called.

app_delegate.rb

class AppDelegate
  def didFinishLaunching(application, withOptions:options)
    Teacup::Appearance.apply

    @window = UIWindow.alloc.initWithFrame(UIScreen.mainScreen.bounds)
    ctlr = MainController.new
    @window.rootViewController = UINavigationController.alloc.initWithRootController(ctlr)
    @window.makeKeyAndVisible

    true
  end

end

That block is called using the UIApplicationDidFinishLaunchingNotification, but that notification is not called until the end of the application(application,didFinishLaunchingWithOptions:launchOptions) method. This is sometimes after your views have been created, and so they will not be styled. If that is the case, call Teacup::Appearance.apply before creating your rootViewController.

Now go use Teacup!

You have enough information right now to go play with Teacup. Check out the example apps, write your own, whatever. But read on to hear about why Teacup is more than just writing layouts and applying styles.

You should also be sure to read the Misc notes section at the bottom. These aren't very well organized, but the information is important. You can learn about features any time, but learning about the "gotcha"s sooner rather than later could save you a lot of time!

Teacup as a utility

When you are prototyping an app it is useful to bang out a bunch of code quickly, and here are some ways that Teacup might help.

You can use all the methods above without having to rely on the entirety of Teacup's layout and stylesheet systems. By that I mean any time you are creating a view hierarchy don't be shy about using Teacup to do it.

UIView and NSView have the style method, which can be used to group a bunch of customizations anywhere in your code. You don't have to pull out a stylesheet to do it.

# Custom Navigation Title created and styled by Teacup
self.navigationItem.titleView = layout(UILabel,
  text:'Title',
  font: UIFont.systemFontOfSize(12),
  )

# Customize contentView in a UITableViewCell dataSource method
def tableView(table_view, cellForRowAtIndexPath:index_path)
  cell_identifier = 'MyController - cell'
  cell = table_view.dequeueReusableCellWithIdentifier(cell_identifier)

  unless cell
    cell = UITableViewCell.alloc.initWithStyle(UITableViewCellStyleDefault,
                        reuseIdentifier: cell_identifier)
    layout(cell.contentView) do
      subview(UIImageView, :image)
    end
  end

  return cell
end

# Use the `style` method on a view to apply your styling. This is a one-shot
# styling.
@label.style(textColor: UIColor.blueColor, text: 'Blue Label')

UITableViews

Teacup is designed to be used in coordination with the controller life cycle, but there are other life cycles that need to be considered as well. UITableViews maintain a "queue" of cells that can be reused, and they need to be restyled when the cell is created and re-used.

The solution is to apply the styles and layout constraints inside the tableView:willDisplayCell:forRowAtIndexPath: delegate method. In your delegate, if you include the Teacup::TableViewDelegate module, you'll get this behavior for free, and if you override this method, you can call super to have the Teacup method run.

class TableViewController < UITableViewController
  include Teacup::TableViewDelegate

  stylesheet :table

  def tableView(table_view, cellForRowAtIndexPath:index_path)
    cell = table_view.dequeueReusableCellWithIdentifier('cell id')

    layout(cell.contentView, :root) do
      cell.title_label = subview(UILabel, :title_label, :text => "title #{index_path.row}")
      cell.details_label = subview(UILabel, :details_label, :text => "details #{index_path.row}")
      cell.other_label = subview(UILabel, :other_label, :text => "other #{index_path.row}")
    end

    return cell
  end

  # This method is implemented by the Teacup::TableViewDelegate.  If you need
  # to implement it, be sure to call super.
  # def tableView(tableView, willDisplayCell:cell, forRowAtIndexPath:indexPath)
  #   super
  # end
end

Constraints and styles get applied before the view appears, even if the cell is reused later.

More Teacup features

There are a few (OK, a bunch) more features that Teacup provides that deserve discussion:

• Styling View Properties
• Orientation Styles
• View Class Additions
• Style Handlers
• Frame Calculations
• Auto-Layout & Motion-Layout
• Stylesheet Extensions

Styling View Properties

Styling a UIView is fun, but a UIView is often composed of many objects, like the layer, or maybe an imageView or textLabel and so on. You can style those, too!

# UITableViewCells have a contentView, a backgroundView, imageView, textLabel,
# detailTextLabel, and a layer! whew!
style :tablecell,
  layer: {  # style the layer!
    shadowRadius: 3
  },
  backgroundView: {  # style the background!
    backgroundColor: UIColor.blackColor
  },
  imageView: {  # style the imageView!
    contentMode: UIViewContentModeScaleAspectFill
  }

Orientation Styles

iOS only

There's more to stylesheets than just translating UIView setters. Teacup can also apply orientation-specific styles. These are applied when the view is created (using the current device orientation) and when a rotation occurs.

Teacup::Stylesheet.new :main do

  # this label hides when the orientation is landscape (left or right)
  style :label,
    landscape: {
      hidden: true
    },
    portrait: {
      hidden: false
    }

end

Combine these styles with Frame Calculations to have you view frame recalculated automatically.

Animation additions

We've already seen the Teacup related properties:

• stylename, the primary style name
• style_classes, secondary style names
• style, apply styles directly

Each of these has a corresponding method that you can use to facilitate animations.

• animate_to_stylename(stylename)
• animate_to_styles(style_classes)
• animate_to_style(properties)

On OS X you have to use the view.animator property to perform animations. This is supported, but it's kind of "hacky".

Style Handlers

This feature is used extensively by sweettea to make a more intuitive stylesheet DSL

Teacup is, by itself, pretty useful, but it really does little more than map Hash keys to UIView setters. That's great, because it keeps the system easy to understand. But there are some methods in UIKit that take more than one argument, or could benefit from some shorthands.

This is where Teacup's style handlers come in. They are matched against a UIView subclass and one or more stylenames, and they are used to apply that style when you use it in your stylesheet.

# this handler adds a `:title` handler to the UIButton class (and subclasses).
Teacup.handler UIButton, :title do |target, title|
  target.setTitle(title, forState: UIControlStateNormal)
end

# ...
subview(UIButton,
  title: 'This is the title'  # <= this will end up being passed to the handler above
  )

layout(UINavigationItem,
  title: 'This is the title'  # <= but this will not!  the handler above is restricted to UIButton subclasses
  )

Other built-in handlers are defined in z_handlers.rb. Another useful one is the ability to make view the same size as its parent, and located at the origin.

style :container,
  frame: :full  # => [[0, 0], superview.frame.size]

Frame Calculations

These are super cool, just don't forget your autoresizingMasks

When positioning views you will often have situations where you want to have a view centered, or 8 pixels to the right of center, or full width/height. All of these relationships can be described using the Teacup.calculate method, which is called automatically in any method that modifies the frame or center.

frame, origin, size
top/y, left/x, right, bottom, width, height
center_x/middle_x, center_y/middle_y, center

Teacup::Stylesheet.new :main do

  style :button,
    left: 8, top: 8,  # easy enough!
    width: '100% - 16',  # woah!  (O_o)
    height: 22

  style :top_half,
    frame: [[0, 0], ['100%', '50%']]
  style :bottom_half,
    frame: [[0, '50%'], ['100%', '50%']]

end

When this code executes, the string '100% - 16' is translated into the formula 1.00 * target.superview.frame.size.width - 16. If the property is related to the height or y-position, it will be calculated based on the height.

The frame calculations must be a string of the form /[0-9]+% [+-] [0-9]+/. If you need more "math-y-ness" than that, you can construct strings using interpolation.

margin = 8

style :button,
  left: margin, top: margin,
  width: "100% - #{margin * 2}",
  height: 22

# just for fun, let's see what it would take to add a margin between these two views.
style :top_half,
  frame: [[0, 0], ['100%', "50% - #{margin / 2}"]]
style :bottom_half,
  frame: [[0, "50% + #{margin / 2}"], ['100%', "50% - #{margin / 2}"]]

One more example: The real power of the frame calculations comes when you remember to set springs and struts. You can have a view "pinned" to the bottom if you remember to set the autoresizingMask.

Teacup::Stylesheet.new :main do

  style :button,
    # fixed width / height
    height: 22, width: 200,
    center_x: '50%',
    top: '100% - 30',  # includes an 8px margin from the bottom
    autoresizingMask: (UIViewAutoresizingFlexibleLeftMargin |
                       UIViewAutoresizingFlexibleRightMargin |
                       UIViewAutoresizingFlexibleTopMargin)
    # see the autoresizing extension below for an even better way to write this.
end

Auto-Layout

This is another much bigger topic than it is given space for here

Teacup includes an Auto-Layout constraint DSL that you can use in your stylesheets. These methods are added to the Stylesheet class, so unless you are in the context of a stylesheet, you will have to create your constraints in longhand (you can still use the Teacup::Constraint class to help you!).

I won't sugar-coat it: Auto-Layout is hard. Much harder than using frames and springs and struts. And honestly, I recommend you try using the Teacup.calculate features mentioned above, they will take you far.

But at the end of the day, once you really understand the auto-layout system that Apple released in iOS 6, you can build your UIs to be responsive to different devices, orientations, and sizes. UIs built with auto-layout not usually need to adjust anything during a rotation. The constraints take care of it all. It's impressive.

Here's a quick example that creates this shape. The edges are bound to the superview's frame.

+-----+----------------+
|     |                |
|  A  |     B          |
|     |          +-----| <\
|     |          |  C  |  |_ 50% of B's height, minus 10 pixels
+-----+----------+-----+ </
^--+--^          ^--+--^
   |_fixed (100)    |_fixed (100)

Teacup::Stylesheet.new do
  style :A,
    constraints: [
      # these first three are all fixed, so super easy
      constrain_left(0),
      constrain_width(100),
      constrain_top(0),
      # here we go, here's a real constraint
      constrain(:bottom).equals(:superview, :bottom),
    ]

  style :B,
    constraints: [
      # B.left == A.right
      constrain(:left).equals(:A, :right),
      # B.height == A.height
      constrain(:height).equals(:A, :height),
      constrain(:right).equals(:superview, :right),
    ]

  style :C,  # <= this looks like a very grumpy style :C
    constraints: [
      constrain_width(100),
      # pin to bottom-right corner
      constrain(:right).equals(:superview, :right),
      constrain(:bottom).equals(:superview, :bottom),
      # 50% B.height - 10
      constrain(:height).equals(:B, :height).times(0.5).minus(10),
    ]

end

Writing views this way will either make your brain hurt, or make the math-nerd in you chuckle with glee. In this example you could go completely with just frame calculation formulas and springs and struts. Your frame code would still be cluttered, just cluttered in a different way.

If you need to reset the list of constraints managed by Teacup, you can call reset_constraints before you add the new styles to a UIView. This can be useful when you need to define a new set of layout constraints for a dynamic set of views.

This works on OS X and iOS, and you don't have to go changing the idea of "top" and "bottom" even though OS X uses reversed frames.

Motion-Layout

If you are using Nick Quaranto's motion-layout gem, you can use it from within any class that includes Teacup::Layout. Then benefit is that the Teacup stylenames assigned to your views will be used in the dictionary that the ASCII-based system relies on.

def teacup_layout
  subview(UIView, :view_a)
  subview(UIView, :view_b)
  subview(UIView, :view_c)

  # if you need to apply these to a different view, or if you want to assign
  # different names to use in the ASCII strings
  # auto(layout_view=self.view, layout_subviews={}, &layout_block)

  auto do
    metrics 'margin' => 20
    vertical "|-[view_a]-margin-[view_b]-margin-[view_c]-|"
    horizontal "|-margin-[view_a]-margin-|"
    horizontal "|-margin-[view_b]-margin-|"
    horizontal "|-margin-[view_c]-margin-|"
  end
end

Stylesheet extensions

Auto-Layout is just one Stylesheet extension, there are a few others. And if you want to write your own, just open up the Teacup::Stylesheet class and start adding methods.

Autoresizing Masks

If you've used the SugarCube uiautoresizingmask methods, you'll recognize these. They are handy, and hopefully intuitive, shorthands for common springs and struts.

In previous versions of Teacup these were available without needing the autoresize prefix. The old methods are still available, but deprecated.

# keeps the width and height in proportion to the parent view
style :container,
  autoresizingMask: autoresize.flexible_width | autoresize.flexible_height

# the same, but using block syntax
style :container,
  autoresizingMask: autoresize { flexible_width | flexible_height }

# the same again, using a shorthand
style :container,
  autoresizingMask: autoresize.fill

The autoresize methods are grouped into four categories: flexible, fill, fixed, and float. The flexible methods correspond 1::1 with the UIViewAutoresizing* constants.

The fill methods (fill,fill_top,fill_bottom,fill_left,fill_right) will stretch the width, or height, or both. The location specifies where the view is pinned, so fill_top will stretch the width and bottom margin, but keep it the same distance from the top (not necessarily at the top, but a fixed distance). fill_right will pin it to the right side, stretch the height, and have a flexible left margin.

The fixed methods pin the view to one of nine locations:

top_left    |  top_middle   |    top_right
------------+---------------+-------------
middle_left |     middle    | middle_right
------------+---------------+-------------
bottom_left | bottom_middle | bottom_right

e.g. fixed_top_left, fixed_middle, fixed_bottom_right

The float methods fill in the last gap, when you don't want your view pinned to any corner, and you don't want it to change size.

# incidentally:
float_horizontal | float_vertical == fixed_middle

Device detection

iOS only

Because the stylesheets are defined in a block, you can perform tests for device and screen size before setting styles. For instance, on an ipad you might want to have a larger margin than on the iphone.

The Stylesheet device methods will help you create these conditions:

Teacup::Stylesheet.new do
  if device_is? iPhone
    margin = 8
  elsif device_is? iPad
    margin = 20
  end

  style :container,
    frame: [[margin, margin], ["100% - #{margin * 2}", "100% * #{margin * 2}"]]
end

Multiple calls to style will add those styles, not replace. So this code works just fine:

Teacup::Stylesheet.new do
  style :logo,
    origin: [0, 0]

  if device_is? iPhone
    style :logo, image: UIImage.imageNamed "small logo"
  elsif device_is? iPad
    style :logo, image: UIImage.imageNamed "big logo"
  end
end

Rotation helpers

iOS only

Because you can animate changes to the stylename or style_classes, you can make it pretty easy to apply rotation effects to a UIView or CALayer. The style_classes property is especially useful for this purpose.

style :container,
  frame: :full

# UIView transforms

style :rotated,
  transform: transform_view.rotate(pi / 2)  # pi and transform_view are methods on Stylesheet

style :not_rotated,
  transform: transform_view.rotate(0)

# CALayer transforms

style :rotated,
  layer: { transform: transform_layer.rotate(pi / 2) }

style :not_rotated,
  layer: { transform: transform_layer.rotate(0) }

These work even better when used with the geomotion methods that extend CGAffineTransform and CATransform3D.

style :goofy,
  transform: CGAffineTransform.rotate(pi / 2).translate(100, 0).scale(2)
style :regular,
  transform: CGAffineTransform.identity

# CALayer uses CATransform3D objects
style :regular,
  layer: {
    transform: CATransform3D.rotate(pi / 2)
  }

Showdown

As a recap, here is a translation of traditional Cocoa code done using Teacup.

No cool tricks here, just some plain ol' Cocoa.

#
# Traditional Cocoa
#
class SomeController < UIViewController

  def viewDidLoad
    @field = UITextField.new
    @field.frame = [[10, 10], [200, 50]]
    @field.textColor = UIColor.redColor
    view.addSubview(@field)

    @search = UITextField.new
    @search.frame = [[10, 70], [200, 50]]
    @search.placeholder = 'Find something...'
    @search.textColor = UIColor.redColor
    view.addSubview(@search)
  end

  # perform the frame changes depending on orientation
  def willAnimateRotationToInterfaceOrientation(orientation, duration:duration)
    case orientation
    when UIInterfaceOrientationLandscapeLeft, UIInterfaceOrientationLandscapeRight
      @field.frame = [[10, 10], [360, 50]]
      @search.frame = [[10, 70], [360, 50]]
    else
      @field.frame = [[10, 10], [200, 50]]
      @search.frame = [[10, 70], [200, 50]]
    end
  end

end

#
# Teacup
#

class SomeController < UIViewController

  stylesheet :some_view

  def teacup_layout
    root(:root)
    subview(UITextField, :field)
    @search = subview(UITextField, :search)
  end

end

Teacup::Stylesheet.new(:some_view) do

  style :root,       # enable landscape rotation (otherwise only portrait is enabled)
    landscape: true  # this must be on the root-view, to indicate that this view is
                     # capable of handling rotations

  style :field,
    left:   10,
    top:    10,
    width:  200,
    height: 50,
    landscape: {
      width: 360  # make it wide in landscape view
    }

  style :search, extends: :field,
    left: 10,
    top: 70,
    placeholder: 'Find something...'

  style UITextField,                # Defining styles based on view class instead
    textColor: UIColor.redColor     # of style name.

end

The Nitty Gritty

Regarding Style Precedence

You need to be careful when extending styles and using orientation styles because the precedence rules take some getting used to. The goal is that you can have all your style code in the stylesheets. But you also need to be able to animate your views, and rotating the device should not go reseting everything.

So here's what happens.

When your controller is loaded, viewDidLoad is called, and that's where Teacup creates the view hierarchy and applies the styles. It is at the end of the method that the styles are applied - not until all the views have been added. The current device orientation will be used so that orientation-specific styles will be applied.

Now Teacup goes quiet for a while. Your app chugs along... until the user rotates the device.

If you have orientation-specific styles, they will get applied. But the original styles (the "generic" styles) will not.

However, there's a way around that, too. If you call restyle! on a UIView, that will reapply all the original stylesheet styles - orientation and generic styles.

With me so far? Orientation styles are reapplied whenever the device is rotated. But generic styles are only applied in viewDidLoad and when restyle! is called explicitly.

How does the :extends property affect things?

If your stylesheet defines orientation-specific styles and "generic" styles, the orientation-specific styles win. But if you extend a style that has orientation-specific styles, your local generic styles will win.

The more "local" styles always win - and that applies to styles that you add using the subview/layout methods, too. The only time it doesn't really apply is if you apply styles using UIView#style or UIView#apply_stylename. Those are one-shot (they can get overwritten when restyle! is called).

There are also times when you either want (or must) override (or add to) the stylesheet styles. For instance, if you want to assign the delegate or dataSource properties, this cannot be done from a Stylesheet. But that's okay, because we have a chance to add these styles in the subview and layout methods.

def teacup_layout
  subview(UITableView, delegate: self)
end

Styles applied here are one-shot. It is the exact same as assigning the stylename and style_classes and then calling style. Because the stylesheet is not necessarily applied immediately, these styles could be overwritten before they take effect.

def teacup_layout
  table_view = subview(UITableView, :tableview, delegate: self,
    font: UIFont.boldSystemFontOfSize(10)  # the stylesheet could override this during rotation
    )
end

def layoutDidLoad
  table_view.apply_stylename(:tableview_init)  # this will only get applied once
end

The idea here is that the closer the style setting is to where the view is instantiated, the higher the precedence.

More examples!

class MyController < UIViewController
  stylesheet :my_sheet
  def teacup_layout
    subview(UILabel, :label, text: 'overrides')
  end
end
Teacup::Stylesheet.new :my_sheet do
  style :generic_label,
    text: 'portrait',
    # these get applied initially, but after being rotated they will not get
    # applied again
    font: UIFont.boldSystemFontOfSize(10),
    textColor: UIColor.grayColor,
    landscape: {
      font: UIFont.boldSystemFontOfSize(12),
      textColor: UIColor.whiteColor,
    }  # this style should add a `portrait` setting that restores the font and color

  style :label, extends: :generic_label,
    font: UIFont.systemFontOfSize(10),  # this will override all the font settings
end

Advanced Teacup Tricks

There are times when you might wish teacup "just worked", but please remember: Teacup is not a "blessed" framework built by Apple engineers. We have access to the same APIs that you do. That said, here are some use-cases where you can most definitely use teacup, but you'll need to do a little more leg work.

Trust your parent view - by using springs and struts

...not autolayout

It's been mentioned a few times in this document that Teacup will create & style views in the viewDidLoad method. That means that the superview property of the controller's view will, necessarily, not be set yet. viewDidLoad is called after the view is instantiated (in loadView), and it hasn't been added as a subview yet.

Auto-Layout is based on the relationship between two views - often a container and child view. It's an amazing system, but if that parent view isn't available, well, you're not gonna have much success.

In the case of a UIViewController your "container" is the self.view property, which by default has sensible springs setup so that it stretches to fill the superview. It's not until you go messing with the self.view property, or are not in the context of a UIViewController that things get hairy.

If this is the case, you should get some pretty obvious warning messages, something along the lines of Could not find :superview.

Including Teacup::Layout on arbitrary classes

I don't know about you, but I often write helper classes for tableviews that appear on many screens in an app. You should not shy away from adding teacup's Layout module to these helper classes.

If you are using your controller as your table view dataSource, the subview and layout methods continue to work as you expect them to. This is for the case when you are using a helper class as the dataSource and/or delegate.

class TableHelper
  include Teacup::TableViewDelegate
  include Teacup::Layout

  stylesheet :table_helper

  def tableView(table_view, cellForRowAtIndexPath:index_path)
    cell_identifier = 'MyController - cell'
    cell = table_view.dequeueReusableCellWithIdentifier(cell_identifier)

    unless cell
      cell = UITableViewCell.alloc.initWithStyle(UITableViewCellStyleDefault
                          reuseIdentifier: cell_identifier)

      layout(cell.contentView) do
        subview(UIImageView, :image)
      end
      # cell.contentView and all child classes will "inherit" the :table_helper stylesheet
    end

    return cell
  end

end

Calculating values using lambda

All styles can accept a proc, and before the style is applied the proc is called and you can calculate a value at runtime. There are times when this is simply convenient, and there are times when it is necessary.

Convenient: when a value is based on some other view's value

# calculate 'backgroundColor' based on another view
style :some_view,
  backgroundColor: ->(view) { view.backgroundColor = view.superview.someOtherColor }

Required: when you need to instantiate an object, like a view

# calculate 'backgroundColor' based on another view
style :some_view,
  # there's no "only run once" idiom in teacup, so we need to make sure not to
  # create this view *every* time :some_view is restyled.
  leftView: ->(view) { view.leftView || UILabel.alloc.initWithFrame(...) }

Sweettea

SugarCube + Teacup = Sweettea

SugarCube was born of a desire to make Teacup stylesheets more readable, less cluttered with Apple's verbose method names and constants. Sweettea takes this a step further, by implementing a wealth of Teacup handlers that translate Symbols to constants and provide useful shorthands.

style :button,
  normal: { image: 'button-white' },
  highlighted: { image: 'button-white-pressed' },
  title: 'Submit',
  shadow: {
    opacity: 0.5,
    radius: 3,
    offset: [3, 3],
    color: :black,
  },
  font: 'Comic Sans'

style :label,
  font: :bold,
  alignment: :center,
  color: :slateblue

Sweettea also offers some convenient styles that you can extend in your base class. You might want to either specify the Sweettea version you are using in your Gemfile, or copy the stylesheet so that changes to Sweettea don't affect your project. Once that projet is at 1.0 you can rely on the styles not changing.

# buttons! :tan_button, :black_button, :green_button, :orange_button,
# :blue_button, :white_button, :gray_button
style :submit_button, extends: :white_button

# label sets more sensible defaults than a "raw" UILabel (like clear background)
style :header, extends: :label

# inputs!  these are not styled, they just setup keyboard and autocomplete
# settings
# :name_input, :ascii_input, :email_input, :url_input, :number_input,
# :phone_input, :secure_input
style :login_input, extends: :email_input
style :password_input, extends: :secure_input

Misc notes

Multiple calls to style with the same stylename combines styles, it doesn't replace the styles.

---

Styles are not necessarily applied immediately. They are applied at the end of the outermost layout/subview method, including the UIViewController##layout block. If you call stylename= or stylesheet= outside a layout/subview block, your view will be restyled immediately.

---

Restyling a view calls restyle! on all child views, all the way down the tree. Much care has been taken to call this method sparingly within Teacup.

---

Any styles that you apply in a layout/subview method are not retained, they are applied immediately, and so the stylesheet can (and usually do) override those styles if there is a conflict. Only styles stored in a stylesheet are reapplied (during rotation or in restyle!).

---

Stylesheets should not be modified once they are created - they cache styles by name (it is a per orientation cache).

---

You can add and remove a style_class using add_style_class and remove_style_class, which will call restyle! for you if style_classes array was changed.

---

If you need to do frame calculations outside of the stylesheet code, you should do so in the layoutDidLoad method. This is not necessary, though! It is usually cleaner to do the frame calculations in stylesheets, either using geomotion, frame calculations, or auto-layout.

---

Within a subview/layout block views are added to the last object in Layout#superview_chain. Views are pushed and popped from this array in the Layout#layout method, starting with the top_level_view. If you include Teacup::Layout on your own class, you do not have to implement top_level_view unless you want to use the subview method to add classes to a "default" target.

---

When UIView goes looking for its stylesheet it does so by going up the responder chain. That means that if you define the stylesheet on a parent view or controller, all the child views will use that same stylesheet by default. It also means you can assign a stylesheet to a child view without worrying what the parent view's stylesheet is.

Caveat! If you implement a class that includes Teacup::Layout, you can assign it a stylesheet. That stylesheet will be used by views created using layout or subview even though your class is probably not part of the responder chain. Saying that UIView inherits its stylesheet from the responder chain is not accurate; it actually uses teacup_responder, which defaults to nextResponder, but it is assigned to whatever object calls the layout method on the view.

---

If you use Teacup::Appearance but it is not styling the first screen of your app (but, strangely, does style all other screens), try calling Teacup::Appearance.apply before creating you create the rootViewController (in your AppDelegate)..

---

The Dummy

If you get an error that looks like this:

Objective-C stub for message `setHidesWhenStopped:' type `v@:c' not
precompiled. Make sure you properly link with the framework or library that
defines this message.

You probably need to add your method to dummy.rb. This is a compiler issue, nothing we can do about it except build up a huge dummy.rb file that has just about every method that you would want to style. There is a [dummy.rb file for iOS][], and one for OS X.

If you need to add this method to your project, please give back to the community by forking teacup and adding this method to the dummy.rb file. It's easy! Create a subclass, define a method called dummy, and call the "not precompiled" message inside it. That will trigger the compiler to include this method signature.

For instance, lets say you are styling a UIPickerView and you get the error:

Objective-C stub for message `setShowsSelectionIndicator:' type ...

You would open up dummy.rb and add the following code:

class DummyPickerView < UIPickerView
private
  def dummy
    setShowsSelectionIndicator(nil)
  end
end

Recompile your project, and you should be good to go!

Teacup is a Community Project!

Teacup was born out of the #rubymotion irc chatroom in the early days of RubyMotion. Its design, direction, and priorities are all up for discussion!

I'm Colin T.A. Gray, the maintainer of the Teacup project. I hope this tool helps you build great apps!