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Feature #13583

Updated by graywolf (Gray Wolf) about 3 years ago

In 2.4, new useful method `Hash#transform_values` was added. I would like to propose also adding matching method `Hash#transform_keys`. 

 ```ruby 
 {a: 1, b: 2}.transform_keys { |k| k.to_s } 
 => {"a"=>1, "b"=>2} 
 ``` 

 What needs to be considered is what to do in case of two keys mapping to the same new key value 

 ```ruby 
 { a: 1, b: 2 }.transform_keys {|_| :same_key } # what should happen? 
 ``` 

 I think using `Hash[]` as model behaviour is a good idea. 

 ```ruby 
 Hash[{ a: 1, b: 2 }.map { |key, value| [:s, value] }] 
 => {:s=>2} 
 ``` 

 it's also how `Hash#transform_keys` works in rails (afaict). 

 This is a follow up feature request to #9970, which seems to be stalled. If the behaviour can be agreed upon, I can try putting together a patch (if no one else wants want to step up).

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