success/failure result object

result.rb

module Result
  class << self
    def success(value)
      Success.new(value)
    end

    def failure(error)
      Failure.new(error)
    end
  end
  
  class Failure
    def initialize(error)
      @error = error
    end
    
    def flat_map
      self
    end

    def map
      self
    end

    def or_else
      yield
    end

    def get_or_else
      yield
    end
    
    def get!
      raise @error
    end

    def for_each
    end
  end

  class Success
    def initialize(value)
      @value = value
    end

    def flat_map
      yield @value
    end

    def map
      Success.new(yield @value)
    end

    def or_else
      self
    end

    def get_or_else
      @value
    end
    
    def get!
      @value
    end

    def for_each(&block)
      flat_map(&block)
      nil
    end
  end

  private_constant :Success, :Failure
end