From: ritchie@...
Date: 2021-03-02T17:48:46+00:00
Subject: [ruby-core:102723] [Ruby master Feature#17663] Enumerator#with, an alternative to Enumerator#with_object

Issue #17663 has been updated by RichOrElse (Ritchie Buitre).


Hanmac (Hans Mackowiak) wrote in #note-4:
> i had a similar problem when i wanted to make Symbol to_proc use parameters, i would have done something like `:to_s.(16)`

Thanks, the implementation of format proc could be anything other than **Integer#to_s** .
I usually define to_proc for my classes, in those scenarios I couldn't use **Symbol#call** .

``` ruby
class UserPresenter < SimpleDelegator
  def initialize(model, view = nil)
    @view = view
    super
  end

  def self.to_proc
    method(:new).to_proc
  end
end

@users = User.all.map.with(view_context, &UserPresenter)
```


----------------------------------------
Feature #17663: Enumerator#with, an alternative to Enumerator#with_object
https://bugs.ruby-lang.org/issues/17663#change-90719

* Author: RichOrElse (Ritchie Buitre)
* Status: Open
* Priority: Normal
----------------------------------------
**Enumerator#with** yields each element along with the arguments
``` ruby
class Enumerator
  def with(*options)
    return to_enum(:with, *options) unless defined? yield

    each do |entry|
      yield entry, *options
    end
  end
end
```

Suppose we have a proc that accepts more than 1 argument.
``` ruby
format = proc do |value, *option|
  value.to_s(*option)
end
``` 
Normally to apply the argument we enclosed it in a block, like so:
``` ruby
(10..15).map { |n| format.(n, 16) } # => ["a", "b", "c", "d", "e", "f"]
```
I found **Enumerator#with_object** method awkward to use.
``` ruby
(10..15).each.with_object(16).map(&format) # => ["a", "b", "c", "d", "e", "f"]
```
Tried simplifying this code further, but **Enumerator#with_object** ignores the given block and just returns the argument.
``` ruby
(10..15).map.with_object(16, &format) # => 16
```
Compare to how concise this line using **Enumerator#with** 
``` ruby
(10..15).map.with(16, &format)  # => ["a", "b", "c", "d", "e", "f"]

```






-- 
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>