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List:       ruby-core
Subject:    [ruby-core:74066] [Ruby trunk Feature#12115] Add Symbol#call to allow to_proc shorthand with argumen
From:       felix.buenemann () gmail ! com
Date:       2016-02-29 21:34:43
Message-ID: redmine.journal-57218.20160229213442.6f05cfa7eeddd68d () ruby-lang ! org
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Issue #12115 has been updated by Felix Bünemann.


Although I don't understand the Japanese, the linked issue, with a similar syntax to \
what Shel vacu proposed above, was rejected by Matz. So probably not too much hope on \
getting this into core…

----------------------------------------
Feature #12115: Add Symbol#call to allow to_proc shorthand with arguments
https://bugs.ruby-lang.org/issues/12115#change-57218

* Author: Felix Bünemann
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
I am a great fan of the `Symbol#to_proc` shorthand when mapping or reducing \
collections:

```ruby
[1,2,16].map(&:to_s)
=> ["1", "2", "16"]
[1,2,16].reduce(&:*)
=> 32
```

I often wish it would be possible to pass an argument to the method when doing this, \
which currently requires a block and is more verbose:

```ruby
[1,2,16].map { |n| n.to_s(16) }
=> ["1", "2", "10"]
# active_support example
{id: 1, parent_id: nil}.as_json.transform_keys { |k| k.camelize :lower }.to_json
=> '{"id":1,"parentId":null}'
```

It would be much shorter, if ruby allowed this:

```ruby
[1,2,16].map(&:to_s.(16))
=> ["1", "2", "10"]
# active_support example
{id: 1, parent_id: nil}.as_json.transform_keys(&:camelize.(:lower)).to_json
=> '{"id":1,"parentId":null}'
```

This can be implemented easily, by adding the `Symbol#call` method:

```ruby
class Symbol
  def call(*args, &block)
    ->(caller, *rest) { caller.send(self, *rest, *args, &block) }
  end
end

```

*Source*: [stackoverflow: Can you supply arguments to the map(&:method) syntax in \
Ruby?](http://stackoverflow.com/questions/23695653/can-you-supply-arguments-to-the-mapmethod-syntax-in-ruby)


**I think this is a rather common use case, so I propose to add `Symbol#call` to the \
Ruby standard library.**



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