From: James Edward Gray II <james@...>
Date: 2007-05-30T23:13:27+09:00
Subject: Re: #respond_to? not working for dynamically generated metho

On May 30, 2007, at 9:08 AM, Brian Candler wrote:

> On Wed, May 30, 2007 at 11:00:14PM +0900, Maurice Gladwell wrote:
>> James Gray wrote:
>>> On May 30, 2007, at 7:53 AM, dblack@wobblini.net wrote:
>>>
>>>> You could of course shoehorn find_by_* into respond_to? for AR
>>>> objects, if you don't mind, essentially, writing method_missing  
>>>> twice
>>>> (once for real, once as a kind of pseudo-static twin).
>>>
>>> I don't really understand this stance.  My opinion is that providing
>>> a method_missing() implementation is a convenient way for a
>>> programmer to define a lot of dynamic methods.  This increases the
>>> messages an object responds to.
>>
>> I must agree with James Edward Gray here.
>>
>> David's contrived example is of course possible, but highly  
>> unlikely in
>> practice; a programmer will generally not code his program into a
>> situation in which he can't be sure whether an object will respond  
>> to a
>> particular message sent to it. That's probably a major reason for  
>> having
>> Object#respond_to?.
>
> As an edge case, consider a DRb client proxy object. Should  
> respond_to? be
> handled locally, or should it be proxied to the server? This  
> involves an
> expensive network round trip.
>
> In many cases it may be cheaper to attempt the call and to rescue a
> NoMethodError, than to have 'respond_to?' perform almost as much  
> work as the
> call you're testing.

I agree with everything you just said and it still doesn't convince  
me respond_to?() should lie.  ;)  Whether or not we use respond_to?()  
in a given situation seems like an entirely different issue to me.

James Edward Gray II