From: Maurice Gladwell <maurice.gladwell@...>
Date: 2007-05-30T20:56:08+09:00
Subject: Re: #respond_to? not working for dynamically generated metho

David wrote:
> [...]
> Basically, to know what's going to happen dynamically, you have to run
> the program and send the messages.

It would be possible to define at writing time the entire range of 
messages that an object will respond to. Here's how:

There are two kinds of messages to which an object responds by something 
that is not a NoMethodError:

1) Those corresponding to defined instance methods.

2) Those that are handled in some way by method_missing.

#1 is already well defined and thus handled by #respond_to?. So if we 
could just define the range of messages recognized by method_missing, we 
could have an object return the entire range of messages to which it 
will respond.

Of course, we don't have standard support for that currently, but we 
could (e.g. with some DSL) declare inside the class definition (e.g. 
above the `def method_missing`) patterns to which method_missing would 
respond.

So for example, in ActiveRecord::Base we would have something like:

responds_to /find_by_.+/

Thus `SomeRailsModel.respond_to? :find_by_name` would have the knowledge 
it needs to return the correct answer: true.

--
M.

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