The value of contexts in DCI

post_creation_context.rb

class PostCreationContext
  def initialize(post)
    @post = post
    @post.extend PostNotifier
    @post.extend PostIndexer
    @post.extend PostCacher
  end

  def execute
    @post.save
    @post.notify
    @post.index
    @post.cache
  end
end

posts_controller.rb

class PostsController < ApplicationController
  def create
    post = Post.new
    post.extend PostNotifier
    post.extend PostIndexer
    post.extend PostCacher
    post.save
    post.notify
    post.index
    post.cache
  end
end

# VS

class PostsController < ApplicationController
  def create
    context = PostCreationContext.new(Post.new)
    context.execute
  end
end

Agreed. But you avoid leaky abstractions.

The leakiness potential is worth not having an extra layer.

What if some code on the persistent layer wants to call delete and by that means "remove from the database" vs. some business logic code that calls delete and means "remove from the user interface"?

This is a scenario that I just don't think will come up. When would you ever need to call a delete method on the extended object and then actually need to delete it in the db? A more real life scenario would be calling an archive method then the delete method.

This is all just experimentation for me. I might switch to composition if it gets painful - we'll see.