一.简单工厂模式
首先来看下工厂模式的原理图：
模式特点：工厂根据条件产生不同功能的类。
程序实例：四则运算计算器，根据用户的输入产生相应的运算类，用这个运算类处理具体的运算。
代码特点：C/C++中的switch...case...分支使用字典的方式代替。
使用异常机制对除数为0的情况进行处理。
Python实现代码如下：
#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: Jason Wang
class Operation:
def GetResult(self):
pass
class OperationAdd(Operation):
def GetResult(self):
return self.op1 + self.op2
class OperationSub(Operation):
def GetResult(self):
return self.op1 - self.op2
class OperationMul(Operation):
def GetResult(self):
return self.op1 * self.op2
class OperationDiv(Operation):
def GetResult(self):
try:
result = self.op1/self.op2
return result
except:
print("error:divided by zero.")
return 0
class OperationUndef(Operation):
def GetResult(self):
print("Undefine operation.")
return 0
class OperationFactory:
operation = {}
operation["+"] = OperationAdd();
operation["-"] = OperationSub();
operation["*"] = OperationMul();
operation["/"] = OperationDiv();
def createOperation(self,ch):
if ch in self.operation:
op = self.operation[ch]
else:
op = OperationUndef()
return op
if __name__ == "__main__":
op = input("operator: ")
opa = input("a: ")
opb = input("b: ")
factory = OperationFactory()
cal = factory.createOperation(op)
cal.op1 = int(opa)
cal.op2 = int(opb)
print(cal.GetResult())