之前有看過《ruby設計模式》，不過漸漸的都忘記了。現在買了一個大話設計模式，看起來不是那么枯燥，順便將代碼用ruby實現了一下。

簡單工廠模式：

# -*- encoding: utf-8 -*-#運算類class Operation attr_accessor :number_a,:number_b  def initialize(number_a = nil, number_b = nil)  @number_a = number_a  @number_b = number_b end  def result  0 endend#加法類class OperationAdd < Operation def result  number_a + number_b endend#減法類class OperationSub < Operation def result  number_a - number_b endend#乘法類class OperationMul < Operation def result  number_a * number_b endend#除法類class OperationDiv < Operation def result  raise '除數不能為0' if number_b == 0   number_a / number_b endend#工廠類class OperationFactory def self.create_operate(operate)  case operate  when '+'   OperationAdd.new()  when '-'   OperationSub.new()  when '*'   OperationMul.new()  when '/'   OperationDiv.new()  end endendoper = OperationFactory.create_operate('/')oper.number_a = 1oper.number_b = 2p oper.result

這樣寫的好處是降低耦合。
比如增加一個開根號運算的時候，只需要在工廠類中添加一個分支，并新建一個開根號類，不會去動到其他的類。

工廠方法模式：

# -*- encoding: utf-8 -*-#運算類class Operation attr_accessor :number_a,:number_b  def initialize(number_a = nil, number_b = nil)  @number_a = number_a  @number_b = number_b end  def result  0 endend#加法類class OperationAdd < Operation def result  number_a + number_b endend#減法類class OperationSub < Operation def result  number_a - number_b endend#乘法類class OperationMul < Operation def result  number_a * number_b endend#除法類class OperationDiv < Operation def result  raise '除數不能為0' if number_b == 0   number_a / number_b endendmodule FactoryModule def create_operation endend#加法工廠class AddFactory include FactoryModule  def create_operation  OperationAdd.new end end#減法工廠class SubFactory include FactoryModule  def create_operation  OperationSub.new endend#乘法工廠class MulFactory include FactoryModule  def create_operation  OperationMul.new end end#除法工廠class DivFactory include FactoryModule  def create_operation  OperationDiv.new end endfactory = AddFactory.newoper = factory.create_operationoper.number_a = 1oper.number_b = 2p oper.result

相比于簡單工廠模式，這里的變化是移除了工廠類，取而代之的是具體的運算工廠，分別是加法工廠、減法工廠、乘法工廠和除法工廠。