Little Things: Introspecting Block Parameters

BlockParameters.rb

class Hash
  module Using
    def using(&block)

      values = block.parameters.map do |type, name|
        self[name]
      end
      block.call(*values)
    end
  end

  include Using
end


hash = {
  first_name: "John",
  last_name:  "Smith",
  age: 35
}

hash.using do |first_name, last_name, age|
  puts "Hello, #{first_name} #{last_name}. #{age}"
end


circle = {
  radius: 5,
  color: "blue"
}

area = circle.using { |radius| Math::PI * radius**2 }

puts area