[rails]controllerのdry for 入門

dry前

class BookController < ApplicationController

  def index
    @books = Book.all
  end

  def show
    @book = Book.find(params[:id])
  end

  def new
    @book = Book.new
  end

  def create
    book = Book.new(params[:book].permit(:title, :author))
    book.save
    redirect_to :root
  end

  def edit
    @book = Book.find(params[:id])
  end

  def update
    book = Book.find(params[:id])
    book.update(params[:book].permit(:title, :author))
    redirect_to :root
  end

  def destroy
    book = Book.find(params[:id])
    book.destroy
    redirect_to :root
  end
end

dry後

class BookController < ApplicationController
  before_action :set_book, only: [:show, :create, :edit, update, :destroy]

  def index
    @books = Book.all
  end

  def show
  end

  def new
    @book = Book.new
  end

  def create
    @book = Book.new(book_params)
    @book.save
    redirect_to :root
  end

  def edit
  end

  def update
    @book.update(book_params)
    redirect_to :root
  end

  def destroy
    @book.destroy
    redirect_to :root
  end

  private
    def set_book

    end

    def book_params
      params[:book].permit(:title, :author)
    end
end

before_actionでset_bookを適用させた。
privateメソッドで、book_paramsを一つにまとめた