Combining Rails controllers in one view

[akiryk]

I'd like to let people add comments to an article and I'd like the comment entry field and save button — as well as previous comments — to appear on the same page as the article itself.

I've got an Article model and a Comment model. Article has_many Comments and Comment belongs_to Article. Article is RESTful; not sure about Comment yet.

In my ArticleController "show" action, I believe I'll need to put some of the same code as I would put in the Comment "new" action. That way, I've got a new comment instantiated in case a user decides to add a comment.

Is there a best practice for this sort of thing -- or a tutorial? Any suggestions?

[ReggieB]

It depends how much coding is shared and how widely you want to make it available. There are two DRY options:

1. Put the shared code into an application method (in application.rb) and then accesses it by calling the method from within each of the controller methods that need to run that code
2. Create a module that contains methods that incorporate the required code and then mixin the code in the controllers where it is required.

If the code is relatively small and needed across many of your controllers, then option 1 is usually best. If the code is relatively large and used by only a small number of controller, then option 2 is probably better. Between these two extremes, it's a case of personal choice as to which to use.

consider these two methods:

a. A method added to application.rb

def add_a_to_b(a, b)
  a + b
end

b. A module created as /lib/subtraction_stuff.rb

module SubtractionStuff

  def subtract_a_from_b(a, b)
    a - b
  end
end

To use the method add_a_to_b within a controller, you'd simply add:

@result = add_a_to_b(1,5)

To use the method subtract_a_from_b you need to do this:

class SomeController < ApplicationController

  include SubtractionStuff

  def show
    @result = subtract_a_from_b(40, 10)
  end

end

That is to mixin the module using an include statement, and then use the method within a controller method.

[lo0ol]

That's actually a really simple way to describe modules in general, Reggie... thanks, it helps clarify an area a bit that I haven't dove into too much yet.

[ReggieB]

Glad you like it. I think worked examples are often the easiest way to explain things.