Ruby中使用设计模式中的简单工厂模式和工厂方法模式

之前有看过《ruby设计模式》，不过渐渐的都忘记了。现在买了一个大话设计模式，看起来不是那么枯燥，顺便将代码用ruby实现了一下。

简单工厂模式：

# -*- encoding: utf-8 -*-

#运算类
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
 end
end

#加法类
class OperationAdd < Operation
 def result
  number_a + number_b
 end
end

#减法类
class OperationSub < Operation
 def result
  number_a - number_b
 end
end

#乘法类
class OperationMul < Operation
 def result
  number_a * number_b
 end
end

#除法类
class OperationDiv < Operation
 def result
  raise '除数不能为0' if number_b == 0
  number_a / number_b
 end
end

#工厂类
class OperationFactory
 def self.create_operate(operate)
  case operate
  when '+'
   OperationAdd.new()
  when '-'
   OperationSub.new()
  when '*'
   OperationMul.new()
  when '/'
   OperationDiv.new()
  end
 end
end

oper = OperationFactory.create_operate('/')
oper.number_a = 1
oper.number_b = 2
p oper.result

这样写的好处是降低耦合。
比如增加一个开根号运算的时候，只需要在工厂类中添加一个分支，并新建一个开根号类，不会去动到其他的类。

工厂方法模式：

# -*- encoding: utf-8 -*-

#运算类
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
 end
end

#加法类
class OperationAdd < Operation
 def result
  number_a + number_b
 end
end

#减法类
class OperationSub < Operation
 def result
  number_a - number_b
 end
end

#乘法类
class OperationMul < Operation
 def result
  number_a * number_b
 end
end

#除法类
class OperationDiv < Operation
 def result
  raise '除数不能为0' if number_b == 0
  number_a / number_b
 end
end


module FactoryModule
 def create_operation
 end
end
#加法工厂
class AddFactory
 include FactoryModule

 def create_operation
  OperationAdd.new
 end
end

#减法工厂
class SubFactory
 include FactoryModule

 def create_operation
  OperationSub.new
 end
end
#乘法工厂
class MulFactory
 include FactoryModule

 def create_operation
  OperationMul.new
 end
end
#除法工厂
class DivFactory
 include FactoryModule

 def create_operation
  OperationDiv.new
 end
end

factory = AddFactory.new
oper = factory.create_operation
oper.number_a = 1
oper.number_b = 2
p oper.result

相比于简单工厂模式，这里的变化是移除了工厂类，取而代之的是具体的运算工厂，分别是加法工厂、减法工厂、乘法工厂和除法工厂。