Controllers / Before Actions

Before Actions

Since edit and update require an existing database record like show we can deduplicate this into a before_action.

A before_action allows you to extract shared code between actions and run it before the action. In the above controller code, @product = Product.find(params[:id]) is defined in three different methods. Extracting this query to a before action called set_product cleans up our code for each action.

This is a good example of the DRY (Don’t Repeat Yourself) philosophy in action.

class ProductsController < ApplicationController
  before_action :set_product, only: %i[ show edit update ]

  def index
    @products = Product.all
  end

  def show
  end

  def new
    @product = Product.new
  end

  def create
    @product = Product.new(product_params)
    if @product.save
      redirect_to @product
    else
      render :new, status: :unprocessable_entity
    end
  end

  def edit
  end

  def update
    if @product.update(product_params)
      redirect_to @product
    else
      render :edit, status: :unprocessable_entity
    end
  end

  private
    def set_product
      @product = Product.find(params[:id])
    end

    def product_params
      params.expect(product: [ :name ])
    end
end

CRUD: Editing Products

Extracting Partials

Files

Preparing Environment

Preparing Ruby runtime
Prepare development database