comparing_with.rb

module ComparingWith
  module InstanceVariables
    def ==(other)
      [self, other].map {|object|
        names = object.instance_variables
        values = names.map {|name| object.instance_variable_get name }
        [names, values].transpose.to_h
      }.reduce(&:==)
    end
  end
end

class Foo
  include ComparingWith::InstanceVariables

  def initialize(a, b)
    @a, @b = a, b
  end
end

puts Foo.new(1, 2) == Foo.new(1, 2) #=> true
puts Foo.new(1, 2) == Foo.new(3, 4) #=> false