readme.md

In map.rb, map is far faster.

In each_with_object.rb, each_with_object is just a tiny bit faster than assign & return.

each_with_object.rb

require 'benchmark/ips'

User = Struct.new(:id, :stuff)
a = Array.new(1000) { |i| User.new(i, stuff: rand(1000)) }

Benchmark.ips do |x|
  x.report('#inject assign&return') do
    a.inject({}) { |memo, i| memo[i.id] = i.stuff; memo }
  end
  x.report('merge') do
    a.inject({}) { |memo, i| memo.merge(i.id => i.stuff) }
  end
  x.report('merge!') do
    a.inject({}) { |memo, i| memo.merge!(i.id => i.stuff) }
  end
  x.report('each_with_object') do
    a.each_with_object({}) { |i, memo| memo[i.id] = i.stuff }
  end
end

map.rb

require 'benchmark/ips'

User = Struct.new(:id, :stuff)
a = Array.new(1000) { |i| User.new(i, stuff: rand(1000)) }

Benchmark.ips do |x|
  x.report('#map') do
    a.map(&:stuff)
  end

  x.report('#each_with_object') do
    a.each_with_object([]) do |user, collection|
      collection << user.stuff
    end
  end
end