Extract ActiveRecord Scope Method

Peer review today lead to a great refactoring opportunity. The pull request centered around allowing signed in site administrators to view unpublished blog posts.

Original

My goal here is to only have the published scope apply if the current_user is not an administrator in both the index and blog_post actions.

class BlogController < SiteController

  def index
    @blog_posts = blog.blog_posts.published
  end

  def blog_post
    @blog_post = blog.blog_posts.published.friendly.find(params[:id])
  end

  private

  def blog
    current_site.blog
  end
end

Initial Attempt

My first attempt is not very clean in the blog_post action.

  • The intent is lost being spread across 3 lines
  • The current_user.try(:administrator?) logic is duplicated across two actions
class BlogController < SiteController

  def index
    if current_user.try(:administrator?)
      @blog_posts = blog.blog_posts
    else
      @blog_posts = blog.blog_posts.published
    end
  end

  def blog_post
    blog_posts = blog.blog_posts
    blog_posts = blog_posts.published unless current_user.try(:administrator?)
    @blog_post = blog_posts.friendly.find(params[:id])
  end

  private

  def blog
    current_site.blog
  end
end

Refactor

And now for the refactor. Here you can see how this really cleaned up.

The ActiveRecord scope has been extracted to a private method named blog_posts_scope

This extracted scope can now be used in the index and blog_post actions and it gets rid of the logic duplication to determine if the current_user is an administrator.

class BlogController < SiteController

  def index
    @blog_posts = blog_posts_scope
  end

  def blog_post
    @blog_post = blog_posts_scope.friendly.find(params[:id])
  end

  private

  def blog_posts_scope
    if current_user.try(:administrator?)
      blog.blog_posts
    else
      blog.blog_posts.published
    end
  end

  def blog
    current_site.blog
  end
end

Peer reviews and refactoring techniques for the win!