Managing Complexity with Presenters
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When creating APIs, you should strive to manage complexity by using plain old ruby objects and presenters. RABL is a view and like all views, one of the first principles of web development is to keep complex logic out of views. Keep complex logic in a well-organized object that is well-testable.
From David's excellent post on presenters, we can see how to simplify complex RABL templates. Take this view as an example:
# post_controller.rb def show @post = Post.find(params[:id]) end # show.rabl object @post attributes :title, :body child :author do |post| attribute :name => :author_name unless post.author == current_user end node :publication_date do |post| if post.status == 'published' post.published_date end end
Simply organize the logic needed in the view within a presenter using Draper and/or plain ruby objects:
# post_presenter.rb class PostPresenter < Draper::Base decorates :post attr_reader :current_user def initialize(post, current_user) super(post) @current_user = current_user end def author_name author.name unless author == @current_user end def publication_date publication_date if status == 'published' end end # post_controller.rb def show @post = PostPresenter.new(Post.find(params[:id]), current_user) end # show.rabl object @post attributes :title, :body, :author_name, :publication_date
Notice that now the logic and complexity is stored in a presenter object and the RABL template is kept clean of complex logic. Keeping complex logic out of views is an important principle in creating maintainable and well-tested applications.
Great articles to read:
I cover most of the above with Testing in isolation, example in RABL on my blog. After writing that, I recently read Objects on Rails and found that Avdi Grimm covers much of the same but explains it better in book format.