From: Joel VanderWerf <vjoel@...>
Date: 2006-11-17T07:38:11+09:00
Subject: Re: #returning and #tap

dblack@wobblini.net wrote:
> Hi --
> 
> On Fri, 17 Nov 2006, Joel VanderWerf wrote:
> 
>> dblack@wobblini.net wrote:
>>> Hi --
>>>
>>> On Fri, 17 Nov 2006, Joel VanderWerf wrote:
>>>
>>>> Coming full circle around the golf course... This last one above is 
>>>> what lead me to prefer #then (== #tap) in the first place:
>>>>
>>>> def foo
>>>>  @foo ||= Foo.new.then do |f|
>>>>    f.bar = "bar"
>>>>  end
>>>> end
>>>>
>>>> Also, #then  avoids the scoping nastiness of #instance_eval.
>>>
>>> I'm not getting the semantics of "then".  Do you mean "then" as in, "I
>>> took off my coat and then sat down", as opposed to then in if/then?
>>
>> Yes. Not much better than #tap, is it? Any ideas...? "and_then"?
> 
> "whereupon" :-)  I guess it's hard to find a name that's general
> enough (as opposed to, say, "post_initialize") but also expressive
> enough.  It does seem a slightly odd technique to me, in any case --
> sort of like saying "Now I'm going to do this: this" instead of just
> going to a new line and saying: "this".  I'm not sure how much of the
> oddness I feel is the technique as opposed to the naming issue.

Does the following technique seem odd?

class Foo
   attr_accessor :a, :b, :c
   def initialize
     yield self if block_given?
   end
end

foo = Foo.new do |f|
   f.a = 1
   f.b = 2
   f.c = 3
end

#then is just a way of using arbitrary classes (or factories) in this 
way. Maybe the name should not emphasize the temporal ("then" or 
"whereupon"); so maybe "tap" is better, or "configured_using".

Btw, I don't think I've ever used #then in more than 5 or 6 places. 
Usually, I just try to define classes like Foo above.

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407