learning aid for the jr devs, passing ruby lambdas as first class args

gistfile1.txt

printer = ->(msg) { puts "#{msg}" }
logger  = ->(msg) { File.open("test.txt", "a") {|f| f.write(msg) } }

class Person

  def initialize(first_name, last_name)
    @first_name, @last_name = first_name,
                              last_name
  end

  def display_name(printer)
    name = "#{@first_name} #{@last_name}"
    printer.call(name)
    name
  end
end

require 'minitest/autorun'
require 'mocha/setup'

require 'stringio'
 
module Kernel
 
  def capture_stdout
    out = StringIO.new
    $stdout = out
    yield
    return out
  ensure
    $stdout = STDOUT
  end
 
end

describe Person do
  subject { Person.new("James", "OKelly")  }
  
  describe "#display_name" do
    subject { Person.new("James", "OKelly").
                display_name(printer) }

    describe "when the printer is a putser" do
      let(:hof) { printer }
      it "must use the putser to print the name" do
        stdout = capture_stdout do
          subject
        end
        stdout.string.must_equal "James OKelly\n"
      end
    end

    describe "when the printer is a logger" do
      let(:hof) { logger }
      it "must use the logger to print the name" do
        subject
        File.read("test.txt").must_equal "James OKelly"
      end
    end

  end

end