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Rails Models

Generating models

$ rails g model User

Associations

belongs_to

has_one

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Arel Cheatsheet on Steroids

A (more) complete cheatsheet for Arel, including NamedFunction functions, raw SQL and window functions.

Tables

posts = Arel::Table.new(:posts)
posts = Post.arel_table # ActiveRecord

Table alias

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Generating Migrations

Migrations are a feature of Active Record that allows you to evolve your database schema over time. Rather than write schema modifications in pure SQL, migrations allow you to use an easy Ruby DSL to describe changes to your tables.

Another way of thinking about them is like a kind of version control (like git) for your application's database - only not as cool as Git (because Git rules).

##Each database starts empty Every database starts empty. Adding information to a database can be described as a series of steps, one after another... Migrations allow developers to save the most important steps like creating tables or adding columns. Later you can rollback to before these changes if something goes wrong, although you might lose data if you do this!

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Rails Migration

http://guides.rubyonrails.org/migrations.html

Migrations methods:

• add_column
• add_index
• change_column
• change_table
• create_table
• drop_table

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ActiveRecord cheat sheet / EXAMPLES

INSTALL 
=======  
$ gem install activerecord
in GEMFILE: gem ‘activerecord’

REQUIRE 
=======  
require ‘active_record’

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# nil? can be used on any Ruby object. It returns true only if the object is nil.
nil.nil?   # => true 
[].nil?    # => false 
{}.nil?    # => false
"".nil?    # => false
" ".nil?   # => false
true.nil?  # => false

# empty? can be used on some Ruby objects including Arrays, Hashes and Strings. It returns true only if the object's length is zero.
nil.empty?   # NoMethodError: undefined method `empty?' for nil:NilClass

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Rails ActiveRecord (association) - Cheatsheet

http://guides.rubyonrails.org/association_basics.html

Types of associations

• belongs_to : TABLE_NAME
• has_one : TABLE_NAME [:through => :TABLE_NAME]
• has_many : TABLE_NAME [:through => :TABLE_NAME]
• has_and_belongs_to_many : TABLE_NAME [:join_table => :TABLE_NAME]

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=Navigating=
    visit('/projects')
    visit(post_comments_path(post))

=Clicking links and buttons=
    click_link('id-of-link')
    click_link('Link Text')
    click_button('Save')
    click('Link Text') # Click either a link or a button
    click('Button Value')

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Pry Cheat Sheet

• Youtube Tutorial 2013

Command Line

• pry -r ./config/app_init_file.rb - load your app into a pry session (look at the file loaded by config.ru)
• pry -r ./config/environment.rb - load your rails into a pry session

Debugger