委托模式的作用是将一个接口的实现委托给另一个内部对象，这使得我们可以用聚合来替代继承，不必用继承的方式去实现具体动作，而把这个具体实现留给聚合的内部对象去实现。
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#include <iostream>
class RealPrinter { // the "delegate"
public:
void print() {
printf("I'll really print something");
}
};
class Printer { // the "delegator"
public:
Printer(){
p = new RealPrinter(); // create the delegate
}
~Printer(){
delete p;
}
void print() {
p->print(); // delegation
}
private:
RealPrinter *p;
};
int main() {
Printer *printer = new Printer();
printer->print();
return 0;
}
class RealPrinter { // the "delegate"
public:
void print() {
printf("I'll really print something");
}
};
class Printer { // the "delegator"
public:
Printer(){
p = new RealPrinter(); // create the delegate
}
~Printer(){
delete p;
}
void print() {
p->print(); // delegation
}
private:
RealPrinter *p;
};
int main() {
Printer *printer = new Printer();
printer->print();
return 0;
}