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Feature #17036

Updated by zechris (Chris Ottrey) over 4 years ago

This is to allow Regexp matches in Ruby 2.7's new experimental Pattern Matching. 

 eg. 
 ```ruby 
   case /(?<a>.)(?<b>.)/.match("xy") 
   in a: "x", b: 
     "a was 'x' and b was matched to #{b.inspect}" 
   end 

   #=> "a was 'x' and b was matched to 'y'" 
 ``` 

 [`MatchData#named_captures`](https://ruby-doc.org/core-2.7.0/MatchData.html#method-i-named_captures) `MatchData#named_captures` is *close* but not close enough as the Hash required from a `deconstruct_keys()` `deconstructed_keys()` method that gets used during Pattern Matching requires symbolized keys. 

 ### **NB. This PR ( https://github.com/ruby/ruby/pull/3333) is WIP as the C code hasn't actually been written yet...** 

 Although, it could be used in the wild now with a refinement of `MatchData` like so: 
 ```ruby 
 module RegexpDeconstructKeys 
   refine MatchData do 
     # Temporary patch in ruby to make tests pass until the code gets re-written in C 
     def deconstruct_keys(*keys) 
       h0 = named_captures.transform_keys(&:to_sym) 
       if keys 
         keys = keys.flatten.compact 
         raise TypeError unless keys.all? { |k| k.is_a?(Symbol) } 
         h0 = h0.slice(*keys) unless keys.empty? 
       end 
       h0.inject({}) { |h, (k, v)| h[k] = v if v; h } 
     end 
     # Temporary patch in ruby to make tests pass until the code gets re-written in C 
   end 
 end 

 using RegexpDeconstructKeys 

 
 case /(?<a>.)(?<b>.)/.match("xy") 
 in a: "x", b: 
   puts "a was 'x' and b was #{b.inspect}" 
 end 

 #=> "a was 'x' and b was matched to 'y'" 
 ``` 
 (tested in `ruby v2.7.1`) 

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