# Rails generate commands

Usage: rails generate GENERATOR_NAME [args] [options].

Use rails generate to list available generators. Alias: rails g.

# Rails Generate Model

To generate an ActiveRecord model that automagically creates the correct db migrations & boilerplate test files for your model, enter this command

rails generate model NAME column_name:column_type

'NAME' is the name of the model. 'field' is the name of the column in the DB table and 'type' is the column type (e.g. name:string or body:text). Check the Remarks section for a list of supported column types.

To setup foreign keys, add belongs_to:model_name.

So say you wanted to setup a User model that has a username, email and belongs to a School, you would type in the following

rails generate model User username:string email:string school:belongs_to

rails g is shorthand for rails generate. This would produce the same result

rails g model User username:string email:string school:belongs_to

# Rails Generate Migration

You can generate a rails migration file from the terminal using the following command:

rails generate migration NAME [field[:type][:index] field[:type][:index]] [options]

For a list of all the options supported by the command, you could run the command without any arguments as in rails generate migration.

For example, if you want to add first_name and last_name fields to users table, you can do:

rails generate migration AddNamesToUsers last_name:string first_name:string

Rails will create the following migration file:

class AddNamesToUsers < ActiveRecord::Migration[5.0]
  def change
    add_column :users, :last_name, :string
    add_column :users, :first_name, :string

Now, apply the pending migrations to the database by running the following in the terminal:

rake db:migrate

rails db:migrate

Note: For even less typing, you can replace generate with g.

# Rails Generate Scaffold

DISCLAIMER: Scaffolding is not recommended unless it's for very conventional CRUD apps/testing. This may generate a lot of files(views/models/controllers) that are not needed in your web application thus causing headaches(bad 😦).

To generate a fully working scaffold for a new object, including model, controller, views, assets, and tests, use the rails g scaffold command.

Then you can run rake db:migrate to set up the database table.

Then you can visit http://localhost:3000/widgets (opens new window) and you'll see a fully functional CRUD scaffold.

# Rails Generate Controller

we can create a new controller with rails g controller command.

$ bin/rails generate controller controller_name

The controller generator is expecting parameters in the form of generate controller ControllerName action1 action2.

The following creates a Greetings controller with an action of hello.

$ bin/rails generate controller Greetings hello

You will see the following output

    create  app/controllers/greetings_controller.rb
      route  get "greetings/hello"
     invoke  erb
     create    app/views/greetings
     create    app/views/greetings/hello.html.erb
     invoke  test_unit
     create    test/controllers/greetings_controller_test.rb
     invoke  helper
     create    app/helpers/greetings_helper.rb
     invoke  assets
     invoke    coffee
     create      app/assets/javascripts/greetings.coffee
     invoke    scss
     create      app/assets/stylesheets/greetings.scss

This generates the following

File Example
Controller File greetings_controller.rb
View File hello.html.erb
Functional Test File greetings_controller_test.rb
View Helper greetings_helper.rb
JavaScript File greetings.coffee

It will also add routes for each action in routes.rb

# Parameters

Parameter Details
-h/--help Get help on any generator command
-p/--pretend Pretend Mode: Run generator but will not create or change any files
field:type 'field-name' is the name of the column to be created and 'type' is the data-type of column. The possible values for 'type' in field:type are given in the Remarks section.

# Remarks

The possible values for 'type' in field:type are:

Data Type Description
:string For smaller pieces of text (usually has a character limit of 255)
:text For longer pieces of text, like a paragraph
:binary Storing data including images, audios and videos
:boolean Storing true or false values
:date Only the date
:time Only the time
:datetime Date and time
:float Storing floats without precision
:decimal Storing floats with precision
:integer Storing whole numbers