From: Rodrigo Rosenfeld Rosas <rr.rosas@...>
Date: 2011-12-16T01:58:45+09:00
Subject: [ruby-core:41681] Documentation of the language itself (syntax, meanings, etc)

Since Ruby is built on top of simple concepts, most of the documentation 
can be read in the Core API and Standard Library API pages.

Unfortunately, I don't see to find any official reference (besides 
mentions to books) about the language syntax itself.

For instance, I wanted to know if this is possible:

class MyViewRenderer < DefaultRender # DefaultRender defines the 
'render' method
   def list
     render_and_return[view: 'not_allowed'] unless allowed?
     render view: 'list' # shouldn't get called
   end

   protected

   def render_and_return
     proc {|*args| render *args; return }
   end

   def allowed?
     false
   end
end

Yeah, I know several folks will point me out that I should be using 
catch-throw for achieving something like this, but that is not the point.

What I'm saying is that I can't find any official reference about the 
meanings of "return", "next" or "break", for instance. Nor can I find 
the reason why such construction is not allowed.

So, what is the reason why the proc with a return can only be called 
inside the method that created it?

Also, is there any documentation source that I'm missing?


Cheers,

Rodrigo.

P.S:
With regards to the catch-throw alternative, it means that I would need 
to have control over the class calling the method from MyViewRenderer, 
which may not be the case... What to do then?

I'm trying to avoid writing ugly code like this:

(render(...); return) if condition?

Or

if condition?
     render(...)
     return
end

Also, unless the API of DefaultRender explicitly says that render will 
always return a truthy value, I couldn't write something like

render(...) and return if condition?