C++编程思想(卷二)：设计模式：职责链模式

#include <iostream>
#include <vector>
#include "../purge.h"
using namespace std;
enum Answer { NO, YES };
class GimmeStrategy {
public:
virtual Answer canIHave() = 0;
virtual ~GimmeStrategy() {}
};
class AskMom : public GimmeStrategy {
public:
Answer canIHave() {
cout << "Mooom? Can I have this?" << endl;
return NO;
}
};
class AskDad : public GimmeStrategy {
public:
Answer canIHave() {
cout << "Dad, I really need this!" << endl;
return NO;
}
};
class AskGrandpa : public GimmeStrategy {
public:
Answer canIHave() {
cout << "Grandpa, is it my birthday yet?" << endl;
return NO;
}
};
class AskGrandma : public GimmeStrategy {
public:
Answer canIHave() {
cout << "Grandma, I really love you!" << endl;
return YES;
}
};
class Gimme : public GimmeStrategy {
vector<GimmeStrategy*> chain;
public:
Gimme() {
chain.push_back(new AskMom());
chain.push_back(new AskDad());
chain.push_back(new AskGrandpa());
chain.push_back(new AskGrandma());
}
Answer canIHave() {
vector<GimmeStrategy*>::iterator it = chain.begin();
while(it != chain.end())
if((*it++)->canIHave() == YES)
return YES;
// Reached end without success...
cout << "Whiiiiinnne!" << endl;
return NO;
}
~Gimme() { purge(chain); }
};
int main() {
Gimme chain;
chain.canIHave();
}