大话设计模式 --- 简单工厂模式
说的是简单的二元数学运算的问题：加减乘除等。
书里是用非C++语言描述的，不过我还是喜欢C++多一点，下面改成了C++版。
操作基类：
class Operation:
{
public:
Operation(): m_numA (0), m_numB(0){}
virtual double GetResult(){return 0;}
void setOperationNum( double numA,double numB )
{
m_numA = numA;
m_numB = numB;
}
private:
double m_numA;
double m_numB;
};
加法类：
class OperationAdd: public Operation
{
public:
virtual double GetResult()
{
return m_numA + m_numB;
}
}
类似实现 减法类 OperationSub 乘法类 OperationMul 等
再实现运算工厂类：
class OperationFactory:
{
public:
Operation * createOperate( const string& operate )
{
Operation* oper;
switch(operate )
{
case "+": oper = new OperationAdd();break;
case "-": oper = new OperationSub();break;
... ...
}
}
}
实际应用：
Operation*oper;
OperationFactory factory;
oper = factory.createOperate("+");
oper->setOperationNum(2,3);
double result = oper->GetResult();
delete oper;