以游戏情景举例：
情景：一个boss发动一个技能时会让自己的喽啰收到随机的增益效果。
提取一下主要需求：
1：随机增益效果
2：通知多个对象
其中1用策略模式+工厂模式来解决，2用观察者模式来解决
先解决1：
* 定义接口：
template<class Obj>class BuffBase {public:virtual void Computer(Obj*) = 0;//计算buff};
* 写几个子类：
template<class Obj>class HealthUpBuff :public BuffBase<Obj> {public:void Computer(Obj* Object) {Object->HealthValue*=2;std::cout << "HealthUp" << std::endl;}};template<class Obj>class MoveUpBuff :public BuffBase<Obj> {public:void Computer(Obj* Object) {Object->MoveSpeed *= 2;std::cout << "MoveUp" << std::endl;}};template<class Obj>class AttackUpBuff :public BuffBase<Obj> {public:void Computer(Obj* Object) {Object->AttackValue *= 2;std::cout << "AttackValueUp" << std::endl;}};
* 建立工厂：
enum BuffName{AttackUp, HealthUp, MoveSpeedUp,AttackSpeedUp};template<class Obj>class BuffFactor {std::unordered_map<BuffName, BuffBase<Obj>*> map;public:BuffFactor() {pushBuff(BuffName::AttackUp, new AttackUpBuff<Obj>());pushBuff(BuffName::HealthUp, new HealthUpBuff<Obj>());pushBuff(BuffName::MoveSpeedUp, new MoveUpBuff<Obj>());pushBuff(BuffName::AttackSpeedUp, new AttackSpeedUpBuff<Obj>());}void pushBuff(BuffName buffName, BuffBase<Obj>* buffBase) {if (buffBase == nullptr) {std::cout << "空指针" << std::endl;return;}if (map.count(buffName) != 0) {std::cout << "对象已存在" << std::endl;return;}map[buffName] = buffBase;}BuffBase<Obj>* GetBuff(BuffName buffName) {return map[buffName];}~BuffFactor()};
解决2：
写接口：
class Monster {public:float HealthValue = 10;float AttackValue = 10;float AttackSpeed = 10;float MoveSpeed = 10;virtual void GetBuff(BuffBase<Monster>* Buff) {Buff->Computer(this);}friend class BuffBase<Monster>;};
boss继承Monster，用list来存储观察者【小喽啰】
class Boss:Monster {std::list<Monster*> monsterVector;public:void pushMonster(Monster* NewMonster) {if (NewMonster == nullptr) return;monsterVector.push_back(NewMonster);}void Devolve() {for (auto t = monsterVector.begin(); t != monsterVector.end(); t++) {(*t)->GetBuff(Factor.GetBuff((BuffName)(rand() % 4)));}}};
完毕
总结一下：
用工厂模式+策略模式解决了随机的buff，即我们需要拓展buff效果时，只需要写继承BuffBase然即可，然后在工厂中增加新的buff即可，Monster和Boss我们是不需要动的，这里是高层和底层都依赖抽象，抽象不依赖底层细节，底层细节依赖抽象。
用观察模式解决了喽啰和boss之间的观察关系。
