Rails generators

Rails comes with many helpful ways to speedup backend development. One really convenient tool are generators.

Generators are used to quickly create your backend structure by taking care of repetitive code, allowing you to focus on the more unique aspects of your application.

There are several different things able to be created with rails generate, the most common ones you might encounter are:

rails generate

controller
migration
model
resource
scaffold
serializer

Model

rails g model <model_name> creates a migration file, including any column names for your table if passed as an argument.
E.g. rails g model Pen brand color price:integer would create the following migration file:

# 20220507194429_create_pens.rb

class CreatePens < ActiveRecord::Migration[6.1]
  def change
    create_table :pens do |t|
      t.string :brand
      t.string :color
      t.integer :price

      t.timestamps
    end
  end
end

model file:

# pen.rb

class Pen < ApplicationRecord
end

and spec file:

# pen_spec.rb

require 'rails_helper'

RSpec.describe Pen, type: :model do
  pending "add some examples to (or delete) #{__FILE__}"
end

Resource

rails g resource Pen brand color price:integer will create all of the above files, along with a serializer:

# pen_serializer.rb

class PenSerializer < ActiveModel::Serializer
  attributes :id, :brand, :color, :price
end

controller:

# pens_controller.rb

class PensController < ApplicationController
end

your routes:

# routes.rb

Rails.application.routes.draw do
  resources :pens
end

and some additional specs.

Scaffold

rails g scaffold Pen brand color price:integer creates all of the above, but adds full CRUD capability for your controller:

# pens_controller.rb

class PensController < ApplicationController
  before_action :set_pen, only: [:show, :update, :destroy]

  # GET /pens
  def index
    @pens = Pen.all

    render json: @pens
  end

  # GET /pens/1
  def show
    render json: @pen
  end

  # POST /pens
  def create
    @pen = Pen.new(pen_params)

    if @pen.save
      render json: @pen, status: :created, location: @pen
    else
      render json: @pen.errors, status: :unprocessable_entity
    end
  end

  # PATCH/PUT /pens/1
  def update
    if @pen.update(pen_params)
      render json: @pen
    else
      render json: @pen.errors, status: :unprocessable_entity
    end
  end

  # DELETE /pens/1
  def destroy
    @pen.destroy
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_pen
      @pen = Pen.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def pen_params
      params.require(:pen).permit(:brand, :color, :price)
    end
end

and more spec files.

Of course it's important to know how all of this code works, and why. However, once you've worked on a few rails projects, generators are a great way to quickly and painlessly create the basic framework for most applications.

Blog

Asher Scott

Model

Resource

Scaffold

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