目的：将“类的功能层次结构”和“类的实现层次结构”分类
类的功能层次：通过类的继承添加功能(添加普通函数)
类的实现层次：通过类的继承实现虚函数
理解：和适配器模式中的桥接方法相同
例子：
class DisplayImpl
{
public:
virtual void open() = 0;
virtual void print() = 0;
virtual void close() = 0;
}; class StringDisplayImpl: public DisplayImpl //实现性扩展
{
public:
void open()
{
cout << "open()" << endl;
} void print()
{
cout << "print()" << endl;
} void close()
{
cout << "close()" << endl;
}
};
class Display
{
DisplayImpl* pImpl; //桥接的核心代码
public:
Display(DisplayImpl* pImpl)
{
this->pImpl = pImpl;
} void print()
{
pImpl->open();
pImpl->print();
pImpl->close();
}
}; class MultiDisplay: public Display //功能性扩展
{
public:
MultiDisplay(DisplayImpl* pImpl): Display(pImpl)
{} void multiPrint()
{
for(int i=0; i<5; i++)
{
print();
}
}
};
int main()
{
Display* d = new Display(new StringDisplayImpl());
d->print(); cout << endl; MultiDisplay* md = new MultiDisplay(new StringDisplayImpl());
md->multiPrint(); return 0;
}