Ruby Results

example_usage.rb

args = # something

Result.try { f(args) }
  .and_then { |f_output| g(f_output) }
  .finally(
    success: proc { |g_output| rended :view },
    failure: proc { |error| flash[:error] = error.to_s }
  )

result.rb

class Result
  def self.try(&failable)
    new(nil).and_then(&failable)
  end

  def and_then(&failable)
    Result.new(failable.call(arg))
  catch error
    Failure.new(error)
  end

  def finally(success: proc {}, failure: nil)
    success.call(arg)
  end

  private
  attr_reader :arg

  def initialize(arg)
    @arg = arg
  end
end

class Failure
  def initialize(error)
    @error = error
  end

  def and_then
    self
  end

  def finally(success: nil, failure: proc {})
    failure(error)
  end

  private
  attr_reader :error
end

Is used on line 7. It's initialized to nil since the first Result in the chain, won't need to use it.