From: matz@...
Date: 2014-02-23T17:05:34+00:00
Subject: [ruby-core:61032] [ruby-trunk - Feature #9552] [Feedback] Module	map!

Issue #9552 has been updated by Yukihiro Matsumoto.

Status changed from Open to Feedback

I am not sure I understand your intention fully, but at least map! reminds us too much of enumerators.
I don't think there's a chance to add map! to module.  Try another name.

Maybe some kind of method (or function) combination natation can help you.

Matz.


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Feature #9552: Module map!
https://bugs.ruby-lang.org/issues/9552#change-45437

* Author: Boris Stitnicky
* Status: Feedback
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
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I would like to beg for `map!` directive in `Module`. I can imitate it with this code:

```ruby
class Module
  def map! **hash, &block
    hash.each_pair { |mapped_method_symbol, original_method_symbol|
      define_method mapped_method_symbol do |*args, &b|
        block.( send original_method_symbol, *args, &b )
      end
    }
  end
end
```

And then

```ruby
class Foo; attr_accessor :name end
class Bar; attr_accessor :name end
class Baz; attr_accessor :name end

class FooBarBazCollection < Array
  def foos; select { |e| e.is_a? Place } end
  def bars; select { |e| e.is_a? Transition } end
  def bazs; select { |e| e.is_a? Arc } end
  map! fn: :foos, barn: :bars, bazn: :bazs do |retval| retval.map &:name end
end
```

I solemnly declare that I have encountered this pattern in my work on Petri net gem sufficiently many times to warrant this meta approach. The above method `#map!` is not perfect, because it makes the "mapped" methods more omnivorous -- accepting even such sets of arguments, for which the originals returned `ArgumentError`. I do not know how to solve this without asking for a core-level solution.



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