Outcomes

outcome.rb

class Outcome
  HANDLER    = "if_"
  HANDLER_RX = /^#{HANDLER}/
  QUERY_RX   = /\?$/

  def self.new(result, *args, &b)
    super.tap { |o| yield o if block_given? }
  end

  def initialize(result, *args)
    @result = result.to_s
    @args   = args
  end

  def announce(listener)
    listener.send(@result, *@args)

    self
  end

  def method_missing(name, *args)
    super if not args.empty?

    case n = name.to_s
    when result_handler then yield(*args); self
    when HANDLER_RX     then self
    when QUERY_RX       then @result == n.sub(QUERY_RX, '')
    else                     super
    end
  end

  private

  def result_handler
    "#{HANDLER}#{@result}"
  end
end

outcome_spec.rb

require 'spec_helper'

describe Outcome do
  subject(:outcome) { Outcome.new(:done) }

  it "yields if passed a block" do
    expect { |b| Outcome.new(:done, &b) }.to yield_control
  end

  it "answers what the outcome was " do
    expect(outcome).to be_done
  end

  it "announces the outcome" do
    mock(self).done

    outcome.announce(self)
  end

  it "executes a code block if it corresponds to the outcome" do
    expect { |b| outcome.if_done(&b) }.to yield_control
  end

  it "does not execute a code block if it doesn't correspond to the outcome" do
    expect { |b| outcome.if_jack(&b) }.not_to yield_control
  end
end