Memo for my beloved students
- Keyboard's shortcuts (Mac)
- Keyboard's shortcuts (LINUX)
- Frequently misunderstood error messages
- NoMethodError: undefined method `some_method' for some_object:SomeType
- TypeError: SomeType can't be coerced into SomeOtherType
- TypeError: no implicit conversion of SomeType into SomeOtherType
- ArgumentError: wrong number of arguments (given N, expected M)
- PG::Error FATAL "myapp_development" does not exist
- ActiveRecord::PendingMigrationError Migrations are pending
- PG::ConnectionBad - could not connect to server: No such file or directory
- NameError: uninitialized constant ClassName
- ResourcesController#action is missing a template for this request format and variant.
- Pundit::NotDefinedError in SomeController#some_action
- Pundit::AuthorizationNotPerformedError in SomeController#some_action
- Pundit::NotAuthorizedError in SomeController#some_action
- Mastering git
- Useful gems
- Going further
{ # alt + (
} # alt + )
[ # alt + shift + (
] # alt + shift + )
| # alt + shift + l
~ # alt + n
\ # alt + /from one program to another # cmd + tab
from one window to another (same program) # cmd + `open a file in current project # cmd + p (or cmd + t)
paste with indentation # cmd + shift + v
move a line upwards in file # ctrl + cmd + ↑
move a line downwards in file # ctrl + cmd + ↓
(un)comment lines # cmd + /
search in file # cmd + f
search in project # cmd + shift + f
add package # cmd + shift + p
add indentation # tab
remove indentation # shift + tab
reach next word # alt + →
reach previous word # alt + ←
reach end of line # cmd + →
reach beginning of line # cmd + ←
close tab # cmd + w
reopen last tab closed # cmd + shift + t
navigate to tab on the right # cmd + alt + →
navigate to tab on the left # cmd + alt + ←
duplicate line # cmd + shift + d
remove line # ctrl + shift + k
split view into two columns # cmd + option + 2
split view into two rows # cmd + option + shift + 2open a new tab # cmd + t
close tab # cmd + w
clear window (keeping history) # ctrl + l
clear window (losing history) # cmd + k
reach next word # alt + →
reach previous word # alt + ←
reach beginning of line # ctrl + a
reach end of line # ctrl + e
erase the whole line # ctrl + u
navigate to tab on the right # cmd + shift + →
navigate to tab on the left # cmd + shift + ←open developer tools (elements) # cmd + alt + i
open developer tools (console) # cmd + alt + j
change docking location # cmd + shift + d
navigate to tab on the right # cmd + alt + →
navigate to tab on the left # cmd + alt + ←
open a new tab # cmd + t
focus on address bar # cmd + l
close tab # cmd + w
reopen last tab closed # cmd + shift + t
hard refresh (clear cache) # cmd + shift + ropen a file in current project # ctrl + p
paste with indentation # ctrl + shift + v
move a line upwards in file # ctrl + shift + ↑
move a line downwards in file # ctrl + shift + ↓
(un)comment lines # ctrl + shift + :
search in file # ctrl + f
search in project # ctrl + shift + f
add package # ctrl + shift + p
add indentation # tab
remove indentation # shift + tab
move text cursor to next word # alt + →
move text cursor to previous word # alt + ←
close tab # ctrl + w
reopen last tab closed # ctrl + shift + t
duplicate line # ctrl + shift + dopen a new tab # ctrl + shift + t
close tab # ctrl + shift + w
clear window # ctrl + L (or type "clear" in terminal)The first advice I'll throw here is to read patiently, entirely, twice the error message when one occurs. This can get tricky when you read it from a tiny terminal window, so start by opening it wide to have a clear look at its face.
# It means that `some_object` **on which you call** `.some_method` is not of the right type.
# You'll get this error if you try to call a `String` instance method on a `Fixnum` for example.
# Its most frequent expression is when `some_object` is nil:
recipe.name
# => NoMethodError: undefined method `name' for nil:NilClass
# `recipe` is nil, it shouldn't!# It means that you're trying to mix apples and oranges.
1 + nil
# => TypeError: nil can't be coerced into Fixnum
2 + "2"
# => TypeError: String can't be coerced into Fixnum# Its cousin.
"2" + 2
# => TypeError: no implicit conversion of Fixnum into String# It means that you're calling a method that takes M parameters with N arguments.
# Either your definition of that method is wrong, either you're calling it with the wrong number of arguments.
def full_name(first_name, last_name)
return first_name.capitalize + " " + last_name.capitalize
end
full_name("boris")
# => ArgumentError: wrong number of arguments (given 1, expected 2)# Just run `rails db:create` in your terminal.# Just run `rails db:migrate` in your terminal.PG::ConnectionBad - could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
# It means that PG did not exit gracefully last time your computer was shut off.
# Run the following in your terminal:
rm /usr/local/var/postgres/postmaster.pid# In most cases, you'll get this error message when you're implementing a gem
# and you forgot to restart your `rails server` after running `bundle install`.# After executing the code in a controller's action, Rails conventionnally
# renders the template named `action.html.erb` in `app/views/resources`.
# It thus means you forgot to generate action's associated view, that you
# misspelled its filename, or that you misplaced it.# The policy is not defined for this controller!
rails g pundit:policy **name_of_the_resource_in_singular**# You need to call `authorize(@some_resource)` in the action (in the controller)
# Make sure you insert this line before saving the resource in your DB!# The rule returns false, you should override ApplicationPolicy's rule by setting it in corresponding ResourcePolicy
# Don't forget to rescue this error with a flash and a redirection at ApplicationController's level!When you want to start a new feature. You have to create a new branch to work from:
(master) git status (CLEAN)
(master) git checkout -b my-feature
You've just finished you feature. Now it's time to make a last commit, create a pull request and go back to master branch:
(my-feature) git add .
(my-feature) git commit -m 'XXXX'
(my-feature) git push origin my-feature
(my-feature) git status (CLEAN)
(my-feature) hub browse
[GO CREATE A PULL REQUEST ON GITHUB]
(my-feature) git checkout master
(master) git pull origin master
(master) git sweep
(master) git checkout -b my-new-feature
When you want to get the latest changes from master on my branch:
(my-feature) git add .
(my-feature) git commit -m 'XXXX'
(my-feature) git status (CLEAN)
(my-feature) git checkout master
(master) git pull origin master
(master) git checkout my-feature
(my-feature) git merge master
When you can't merge a PR due to conflicts in an unmergeable_branch, follow this process:
# first make sure your git status is clean on your current branch
git status # if not clean, add and commit your work
# go to your local master branch
git checkout master
# update your master branch locally with github's master
git pull origin master
# go back to unmergeable_branch
git checkout unmergeable_branch
# merger master in unmergeable branch to solve conflicts locally
git merge master
# now you've fetched all conflicts locally, time to solve them
# open sublime and solve conflicts (locate them with cmd + shift + f <<<<<<<)
# commit your code
git add .
git commit -m "conflict solving"
git push origin unmergeable_branch
# open your PR on github to merge it
hub browse
# merge your PR on github
# go back to your terminal and update your local master with merged files
git checkout master
git pull origin master
# create a new branch for next feature
git checkout -b next_featureWhen you committed some changes to master and wanted to commit them to a new branch, follow this process:
# create a new branch from the current state of master
git checkout -b some-new-branch-name
# remove the commit from the master branch
git checkout master
git reset HEAD~ --hard
# go back to your new branch
git checkout some-new-branch-name
# your commit lives in this branch now
# if you want to make sure it does...
git push origin some-new-branch-name
# ...go check it out by yourself
hub browsePerfect for like / upvote / save to wishlist features!
A good framework to handle notifications. Check this railscast out to set it up in your project!