[ruby-core:102723] [Ruby master Feature#17663] Enumerator#with, an alternative to Enumerator#with_object
From:
ritchie@...
Date:
2021-03-02 17:48:46 UTC
List:
ruby-core #102723
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"]
```
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