From: "Dan0042 (Daniel DeLorme)" <noreply@...>
Date: 2021-11-08T15:45:50+00:00
Subject: [ruby-core:105968] [Ruby master Feature#18276] `Proc#bind_call(obj)` same as `obj.instance_exec(..., &proc_obj)`

Issue #18276 has been updated by Dan0042 (Daniel DeLorme).


Eregon (Benoit Daloze) wrote in #note-10:
> I'd assume on that object's singleton class like `instance_exec`, but I guess it's not the only possibility.

I would assume the same thing; it would be pretty strange if this defined a `foo` method on class C.

But it's interesting how instance_eval/instance_exec automatically creates a singleton_class, I wasn't aware of that before.

```ruby
p ObjectSpace.each_object(Class).count #=> 363
Object.new.instance_eval{ }
p ObjectSpace.each_object(Class).count #=> 364
Object.new.instance_exec{ }
p ObjectSpace.each_object(Class).count #=> 365
```

It looks like the singleton_class is eagerly created just in case the eval'd block contains a `def`. But it shouldn't be too hard to fix that to lazily create the singleton_class when needed.

----------------------------------------
Feature #18276: `Proc#bind_call(obj)` same as `obj.instance_exec(..., &proc_obj)`
https://bugs.ruby-lang.org/issues/18276#change-94515

* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
----------------------------------------
`Proc#bind_call(obj)` same as `obj.instance_exec(..., &proc_obj)`

```ruby
proc_obj = proc{|params...| ...}
obj.instance_exec(params..., &proc_obj)
```

is frequent pattern.

```
$ gem-codesearch 'instance_exec.+\&' | wc -l
9558
```

How about to introduce new method `Proc#bind_call`?

```ruby
class Proc
  def bind_call obj, *args
    obj.instance_exec(*args, &self)
  end
end

pr = ->{ p self }
pr.bind_call("hello") #=> "hello"
pr.bind_call(nil)     #=> nil
```

It is similar to `UnboundMethod#bind_call`.

----

My motivation;

I want to solve shareable Proc's issue https://bugs.ruby-lang.org/issues/18243 and one idea is to prohibit `Proc#call` for shareable Proc's, but allow `obj.instance_exec(&pr)`. To make shortcut, I want to introduce `Proc#bind_call`.

`UnboundProc` is another idea, but I'm not sure it is good idea...

Anyway, we found that there are many usage of `instance_exec(&proc_obj)`, so `Proc#bind_call` is useful not for Ractors.



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>