From: ES <ruby-ml@...>
Date: 2005-03-23T08:09:20+09:00
Subject: Re: RCR 296: Destructive methods return self


In data 3/22/2005, "Ben Giddings" <bg-rubytalk@infofiend.com> ha
scritto:

>Yukihiro Matsumoto wrote:
>>   (2) current bang methods are bad because they work most of the
>>       cases, and fail if no change has made.  thus let us make bang
>>       methods return something other than self, boolean for example,
>>       to fail always.  this forces no chaining of bang methods.
>
>I think this one is the most consistent way of doing things.  In a way,
>using chaining with receiver-modifying methods doesn't make sense.  You
>really don't want to modify the return value of the method, you want to
>modify the original object. 

That doesn't make any sense unless you mean that if I want 'hello' to
become 'Hello', these are really two objects instead of the latter
being a modification of the first? But even in that case, would you
say that modifying class Test's state should also create a new object?

> I think the main reaon people want to chain
>bang methods is that they don't like having to type the variable a lot
>of times.
>
>the_config_string_for_foo = $stdin.gets
>the_config_string_for_foo.strip!.downcase!
>
>is easier to type than
>
>the_config_string_for_foo = $stdin.gets
>the_config_string_for_foo.strip!
>the_config_string_for_foo.downcase!
>
>But it seems to me that what people are really looking for is a way to
>apply multiple methods to an object without having to retype it's name:
>
>the_config_string_for_foo = $stdin.gets
>the_config_string_for_foo.apply { strip!; downcase! }
>
>This has been proposed a few times, I think.  I can't remember how you
>(Matz) felt about it.  Is the reason Ruby doesn't have a way to do it
>because you don't like the idea, or you were hoping for consensus on the
>exact method of doing it?
>
>>   (4) add some kind of reference counting, and if the receiver is
>>       referenced from only one place, modify the receiver in place, to
>>       gain performance.
>
>This sounds like "more work for Matz", but also a really good solution.
>  Most of the time people only want bang methods for efficiency.  If
>that weren't an issue then it would be even easier to have the
>bang-methods return boolean (modified / not modified) and then people
>could choose the method based on what they were after (chaining vs. "was
>something changed") and not based on efficiency.
>
>Ben

E