From: Josh Susser <josh@...>
Date: 2007-11-13T04:03:34+09:00
Subject: Re: alias_method :tap, :affect

Rick Denatale wrote:
> On Nov 12, 2007 12:58 PM, Josh Susser <josh@hasmanythrough.com> wrote:
>>
>> The K-combinator is all about side-effecting the receiver object, so
>> "affect" seems like a meaningful name for that functionality (whereas
>> "effect" would be wrong!).  "tap" is still cute, and rhymes with "map",
>> so having both seems like a good Rubyish way to go.
> 
> Of course, active-support also defines the same method as 
> Object#returning

Not exatcly.  #tap works on the receiver, #returning works on an 
argument.  #tap is more object-oriented IMO.

returning("foo") { |s| s << "bar" }
"foo".affect { |s| s << "bar" }

> I'm not sure how the Smalltalk intro ties in here. 

It's just to say how awsome methods that end in "ect" are, and why :-)

> I can't recall a
> method implementation of the k-combinator in common use in Smalltalk,
> in most cases the message cascade syntax ending with an invocation of
> #yourself, would serve the cases where the k-combinator is used:
> 
> Ruby
> 
>    a = MyObject.new.tap do |o|  # or returning, or affect
>         o.foo = 1
>         o.bar = "whatever"
>    end
> 
>  Smalltalk
>    a = MyObject.new foo: 1;
>                                     bar: "whatever";
>                                     yourself
> 
> For Rubyists unfamiliar with Smalltalk, the message cascade triggered
> by the ; meant send the message after the ; to the receiver of the
> last message.  Object#yourself was defined to return the receiver, and
> was not typically overridden.

That's exactly right. Cascaded messages were cool, and came right out of 
the stack machine nature of Smalltalk's bytecodes. And I've often longed 
for a #yourself method in Ruby, but usually only to get to the target of 
a proxy object.

> --
> Rick DeNatale
> 
> My blog on Ruby
> http://talklikeaduck.denhaven2.com/

--
Josh Susser
http://blog.hasmanythrough.com

-- 
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