content_for vs yield in partials

Question

In rails 3.0 with HAML (3.1.4) I have

1. some template-like partial, like _template.html.haml:

   .panel.top
     = yield :panel_top
   
   .conte         
   
   
           

Answer 1

From Rails 3.0 to Rails 3.2 content_for was really changed:

3.0:

def content_for(name, content = nil, &block)
    content = capture(&block) if block_given?
    @_content_for[name] << content if content
    @_content_for[name] unless content
end

3.2:

def content_for(name, content = nil, &block)
  if content || block_given?
    content = capture(&block) if block_given?
    @view_flow.append(name, content) if content
    nil
  else
    @view_flow.get(name)
  end
end

This shows us, that from 3.2 content_for works for showing/inserting content too, not only store it for named section.

Also, if you make an attempt to debug yield logic you'll se that it yields before content_for is correctly initialized.

So, leaving fragment caching out of this discussion I can conclude that content_for is preferrable way to insert named sections anywhere except top-level layouts. In helpers and other situations yield should render wrong results.