设计模式之- 状态模式（State Pattern）

#include<iostream>
#include<string>

using namespace std;

class State;

class Context {//上下文环境，拥有状态
    State* state;
public:
    Context(){
        state = nullptr;
    }
    void setState(State* state){
        this->state = state;     
    }
    State* getState(){
        return state;
    }
};



class State {//状态接口，可扩展出多种不同的状态
public:
    virtual void doAction(Context* context) = 0;
    virtual string toString() = 0;
};



class StartState :public State {//具体的状态，doAction方法能够以当前状态直接影响上下文
public:
    void doAction(Context* context) {
        cout<<"Player is in start state"<<endl;
        context->setState(this); 
    }

    string toString(){
        return "Start State";
    }
};



class StopState :public State {
public:
    void doAction(Context* context) {
        cout<<"Player is in stop state"<<endl;
        context->setState(this); 
    }

    string toString(){
        return "Stop State";
    }
};


class StatePatternDemo {
public:
    static void method() {
        Context* context = new Context();//上下文环境

        StartState* startState = new StartState();//第一次改变状态
        startState->doAction(context);
        cout<<context->getState()->toString()<<endl;

        StopState* stopState = new StopState();//第二次改变状态
        stopState->doAction(context);
        cout<<context->getState()->toString()<<endl;
    }
};


int main(int argc,char** argv){
    StatePatternDemo::method();
}