Yield and default case || do not output default case

Question

I have a simple yield use case and for some unknown reason the default case is never shown:

In my super_admin layout I have:

<%= yield :body_id || \'s         


        

Answer 1

Why no test if there are a content_for or not define in view compilation.

In the content_for code we can see :

def content_for(name, content = nil, &block)
  ivar = "@content_for_#{name}"
  content = capture(&block) if block_given?
  instance_variable_set(ivar, "#{instance_variable_get(ivar)}#{content}".html_safe)
  nil
end

So in your case, the @content_for_body_id is define if a content_for is in your view.

You can made :

<%=  instance_variable_defined?('@content_for_body_id') ? yield(:body_id) : 'super_admin_main' %>

If you prefere you can generate an helper after

def yield_or(part, result)
  instance_variable_defined?("@content_for_#{part}") ? instance_variable_get("@content_for_#{part}") : result
end

and call it in your view by

<%= yield_or(:body_id, 'super_admin_main') %>

It's works only with Rails 2.3.x

In Rails 3 :

there are this method content_for?