rails_gems.md

Gems that make Rails tick:

ActiveSupport: compatibility library, includes methods that change words from single to plural, or CamelCase to snake_case. Better time/date support than Ruby standard library.

ActiveModel: hooks features into your models.

ActiveRecord: Object-Relational Mapper (ORM), maps Ruby objects to your SQL database. Makes working with data way easier.

ActionPack: does the routing. Maps incoming URL to controllers and actions. Passes instance variables between controllers and views. Can use different templates like erb or haml.

ActionMailer: used to send out email, has text-based templates and not regular web-page templates.

Making Rails/Ruby Gems:

One common pattern seen in a lot of gems is the ! at the end of method calls that will raise an error if not executed properly. As I studied the slugged gem today I found how easy it is to implement those methods in my own gems. Here is an example that illustrates that very well:

def find_using_slug(slug)
  slug = slug.to_s
  value = nil
  value ||= find_by_id(slug.to_i) if slug =~ /\A\d+\Z/
  value ||= with_cached_slug(slug).first
  value ||= find_using_slug_history(slug) if use_slug_history
  value.found_via_slug = slug if value.present?
  value
end

def find_using_slug!(slug)
  find_using_slug(slug) or raise ActiveRecord::RecordNotFound
end

Essentially all you're doing is calling the original method (the non-bang version) and adding an or raise ActiveRecord::RecordNotFound error if nothing is returned.