DRY-ing your Rails controller with filters

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Ever noticed how all CRUD methods on each controller starts with the same line: @item = Model.find(params[:id]) ?

Hey! why not use filter so we don’t repeat ourselves ?

class PostsController < ApplicationController
  before_filter :find_post,   nly => [:show, :edit, :update, :destroy]

  def index
    @posts = Post.find(:all)
  end

  def show
  end

  def new
    @post = Post.new
  end

  def edit
  end

  def create
    @post = Post.new(params[:post])

    if @post.save
      flash[:notice] = 'Post was successfully created.'
      redirect_to post_url(@post)
    else
      render :action => "new"
    end
  end

  def update
    if @post.update_attributes(params[:post])
      flash[:notice] = 'Post was successfully updated.'
      redirect_to post_url(@post)
    else
      render :action => "edit"
    end
  end

  def destroy
    @post.destroy

    redirect_to posts_url
  end

  private
    def find_post
      @post = Post.find(params[:id])
    end
end

The cool thing about this is, if you decide to switch to using model name in the url, you’ll only have one line to change!

It’s a small step for Rails, but a great step towards honouring the DRY principle:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
- The Programatic Programmer

DRY-fulness we salute you!

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