chainofreponsibility.cpp

来自「C++编程思想的源代码。需要的朋友就下载吧。都是已经写好了的源代码。」· C++ 代码 · 共 77 行

//: C10:ChainOfReponsibility.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// The approach of the five-year-old.
#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();
} ///:~