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Rails Generator CheatSheet

Cheat Sheets are greate but they are not a substitute for learning the framework and reading the documentation as we most certainly have not covered every potential example here. Please refer to the Rails Command Line Docs for more information.

Command Line Generator Info


You can get all of this information on the command line.

rails generate with no generator name will output a list of all available generators and some information about global options. rails generate GENERATOR --help will list the options that can be passed to the specified generator.

Rails Generate Examples

Create a Resource

rails generate scaffold Post name:string title:string content:text

Generate Models

rails generate model Post title:string body:text published:boolean

Scaffold with ERB and API namespaced to /api/v1

    rails g scaffold categories name:string image:string description:text status:boolean  -c=scaffold_controller
    rails g scaffold_controller api/v1/categories name:string image:string description:text status:boolean  --api --model-name=Category

Add Column to Existing Model

rails generate migration AddFieldToModel field:type

Column Types

:primary_key, :string, :text, :integer, :float, :decimal, :datetime, :timestamp, :time, :date, :binary, :boolean

Adding a Unique Property to a Field

rails generate scaffold Post name:string title:string content:text slug:string:uniq

Many to Many Relationship (Reference)

Remember that you do not want an id for the join table, so make sure to add :id => false |t|

create_table assemblies_parts, :id => false do |t|
  t.integer :assembly_id
  t.integer :part_id

If you use rails

rails generate model Assemblies_parts assembly:references part:references

you will have two indexes, but what you want is

add_index :assemblies_parts, [:assembly_id, :part_id], :unique => true

For Rails 5 use create_join_table instead.

Adding Modifiers (Reference)

Modifiers are inserted through curly braces and they allow you to include things such as null and limit.

Add an age to a Friend with a limit

rails g model friend age:integer{2}  

Add a price to a product with 2 decimals

rails g model product 'price:decimal{10,2}'  	

Would result in a migration with a scale of 2 and percision of 10

class CreateProducts < ActiveRecord::Migration
  def change
    create_table :products do |t|
      t.decimal :price, precision: 10, scale: 2
      t.timestamps null: false

Create a new model with a reference to another model (Reference)

rails g model Supplier name:string
rails g model Product name:string:index sku:string{10}:uniq count:integer description:text supplier:references popularity:float 'price:decimal{10,2}' available:boolean availableSince:datetime image:binary	

Resulting migrations:

class CreateSuppliers < ActiveRecord::Migration
  def change
    create_table :suppliers do |t|
      t.string :name

      t.timestamps null: false

class CreateProducts < ActiveRecord::Migration
  def change
    create_table :products do |t|
      t.string :name
      t.string :sku, limit: 10
      t.integer :count
      t.text :description
      t.references :supplier, index: true, foreign_key: true
      t.float :popularity
      t.decimal :price, precision: 10, scale: 2
      t.boolean :available
      t.datetime :availableSince
      t.binary :image

      t.timestamps null: false
    add_index :products, :name
    add_index :products, :sku, unique: true

Polymorphism (Reference)

Suppose your building a collaborative app (like Pivotal Tracker and you want to add comments to projects, tasks, and attachments. You can do that by making comments polymorphic.

rails g model Comment body:text commentable:references{polymorphic}:index  

Column Defaults (Reference)

Default migration generator does not handle default values (column modifiers are supported but do not include default or null), but you could create your own generator.

You can also manually update the migration file prior to running rake db:migrate by adding the options to add_column:

add_column :tweet, :retweets_count, :integer, :null => false, :default => 0

... and read Rails API

Rspec Generators


rails generate rspec:model widget

will create a new spec file in spec/models/widget_spec.rb

The same generator pattern is available for all specs:


Generating specific views

rails g rspec:view widget index edit new show
      create  spec/views/widget
      create  spec/views/widget/index.html.erb_spec.rb
      create  spec/views/widget/edit.html.erb_spec.rb
      create  spec/views/widget/new.html.erb_spec.rb
      create  spec/views/widget/show.html.erb_spec.rb

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@lbraun lbraun commented Jun 26, 2019

Super helpful, thank you! Just a note: you've got this in there twice:


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Owner Author

@cdesch cdesch commented Jun 28, 2019

You're welcome @ibraun. I fixed it.


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@kcamcam kcamcam commented Jan 21, 2021

I appreciate the time you put into making this. Thank you 🙂


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@joshtune joshtune commented Jan 23, 2021

very helpful

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