Ruby library function to transform Enumerable to Hash

Consider this extension to Enumerable:

module Enumerable

  def hash_on
    h = {}
    each do |e|
      h[yield(e)] = e
    end
    h
  end

end

It is used like so:

people = [
  {:name=>'fred', :age=>32},
  {:name=>'barney', :age=>42},
]
people_hash = people.hash_on { |person| person[:name] }
p people_hash['fred']      # => {:age=>32, :name=>"fred"}
p people_hash['barney']    # => {:age=>42, :name=>"barney"}

Is there a built-in function which already does this, or close enough to it that this extension is not needed?

Enumerable.to_h accepts either a sequence of [key, value]s or a block for converting elements into a Hash so you can do:

people.to_h {|p| [p[:name], p]}

The block should return a 2-element array which becomes a key-value pair in the returned Hash. If you have multiple values mapped to the same key, this keeps the last one.

In versions of Ruby earlier than 3, you'll need to convert with map first before calling to_h:

people.map {|p| [p[:name], p]}.to_h