[ruby-core:65176] [ruby-trunk - Feature #10095] Object#as

Issue #10095 has been updated by Matthew Kerwin.


Jihwan Song wrote:
> I realized that what is desired here is somewhat different than what can be achieved using class_eval, instance_eval and/or yield.
> 
> What is really desired is a way to define an unnamed instance method that has access only to public methods, that gets defined immediately and disappears(undefined) right after it was invoked once.

What you're requesting is drastically different from the original proposal (i.e. a version of #tap that returns the result of the block, rather than the receiver). You should open a new ticket for it, if you want to pursue it.

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Feature #10095: Object#as
https://bugs.ruby-lang.org/issues/10095#change-49015

* Author: Akira Matsuda
* Status: Open
* Priority: Normal
* Assignee: 
* Category: core
* Target version: current: 2.2.0
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We've had so many times of feature requests for a method similar to Object#tap that doesn't return self but returns the given block's execution result (e.g. #7388, #6684, #6721 ).

I'm talking about something like this in Ruby of course:
Object.class_eval { def as() yield(self) end }

IIRC Matz is not against introducing this feature but he didn't like any of the names proposed in the past, such as embed, do, identity, ergo, reference, yield_self, itself, apply, map, tap!, etc.

So, let us propose a new name, Object#as today.
It's named from the aspect of the feature that it gives the receiver a new name "as" a block local variable.
For instance, the code reads so natural and intuitive like this:

(1 + 2 + 3 + 4).as {|x| x ** 2}
=> 100

Array.new.as {|a| a << 1; a << 2}
=> [1, 2]

---Files--------------------------------
itself-block.patch (1.35 KB)


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