From: Todd Benson <caduceass@...>
Date: 2008-01-18T09:01:47+09:00
Subject: Re: Ruby syntax in "respond_to do |format| line -- can clarify?

On Jan 17, 2008 11:34 AM, Andrew Timberlake <andrew@andrewtimberlake.com> wrote:

> Joshua
>
> respond_to is the method, it provides the block with the format object.
> Within the block, you are calling the methods html and xml on the format object supplied.
> Rather than a loop, the block is more like a callback function that accepts a format object as a parameter.
> The format object now understands that it can respond with either html or xml output.
> Rails then uses the Accepts header of the calling client (browser etc) to decide which of the formats to return.
> You can also append .html or .xml to the url to force one or the other format.
>
> Hope that helps
>
> Andrew Timberlake
> andrew@andrewtimberlake.com
> 082 415 8283
> skype: andrewtimberlake
>
> "I have never let my schooling interfere with my education."
>                                                 --Mark Twain

To illustrate this in a _very_ simple way...

# the following method is akin to what is already defined by rails
(#respond_to, which is much more complicated, of course)
def foo( &block )
  block.call( 42 )
end

# the code you execute
foo do |number|          # 42 is thrown into your block
  puts number
  puts number * 2
end

In a similar way, the object named "format" (or whatever you want to
name it) is thrown into your block by the framework.

At least, that's how I think rails handles it.  I've never used the
method recently, myself, and unfortunately I don't have rails handy at
the moment.

Todd