Issue #10208 has been updated by Shyouhei Urabe.


We looked at this issue at yesterday's developer meeting and had consensus that there is no other example of to_* method that takes a block.  Introducing such new concept seems too risky.

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Feature #10208: Passing block to Enumerable#to_h
https://bugs.ruby-lang.org/issues/10208#change-59705

* Author: Yutaka HARA
* Status: Open
* Priority: Normal
* Assignee: 
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Now that we can convert 'a list of [key, value] pairs' into a hash with Enumerable#to_h,
how about make it take a block to specify 'how to convert each element into a [key, value] pair'? 

Example:

~~~
# Convert users into an {id => name} hash
users.map{|u| [u.id, u.name]}.to_h
    вн
# Convert users into an {id => name} hash
users.to_h{|u| [u.id, u.name]}
~~~

This could also be a solution for these feature requests:

* Feature #6669 A method like Hash#map but returns hash

  hsh.apply{|k, v| [k.to_s, v]}
  == hsh.to_h{|k, v| [k.to_s, v]}

* Feature #7793 New methods on Hash
  Feature #9970 Add `Hash#map_keys` and `Hash#map_values`

  hsh.map_k(&:to_s)
  == hsh.to_h{|k, v| [k.to_s, v]}
  hsh.map_v(&:to_i)
  == hsh.to_h{|k, v| [k, v.to_i]}
  hsh.map_kv(&block)
  == hsh.to_h(&block)




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