Rails Generator Cheatsheet
Tags: rails, cheatsheet
Published: 2019-03-14 20:21:56

---
title: Rails Generator Cheatsheet
published: true
description: Rails Generator Cheatsheet
tags: rails,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](http://guides.rubyonrails.org/command_line.html) for more information.

## Command Line Generator Info

[Reference](https://stackoverflow.com/questions/12900170/is-there-a-reference-cheat-sheet-for-rails-generate-command)

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](https://stackoverflow.com/questions/5322067/generating-a-model-with-many-to-many-in-ruby-on-rails))

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
end
```

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](http://www.chrisjmendez.com/2016/07/01/rails-cheatsheet/))

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
    end
  end
end
```

	
#### Create a new model with a reference to another model ([Reference](https://www.ralfebert.de/snippets/ruby-rails/models-tables-migrations-cheat-sheet/))

	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
    end
  end
end

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
    end
    add_index :products, :name
    add_index :products, :sku, unique: true
  end
end
```

### Polymorphism ([Reference](http://www.chrisjmendez.com/2016/07/01/rails-cheatsheet/))

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](https://stackoverflow.com/questions/6167994/assigning-default-value-while-creating-migration-file))

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](http://api.rubyonrails.org/)

## Rspec Generators
 [Documentation](https://relishapp.com/rspec/rspec-rails/docs/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:
```
scaffold
model
controller
helper
view
mailer
observer
integration
feature
job
```
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
```
-[Article](https://gist.github.com/cdesch/2f8de645cad1d83aa251c0a20b0f7097)