状态模式之观察者模式

题目

类图

Java

Investor接口

package com.gazikel;

public interface Investor {

    void update(float range);
}

Subject接口

package com.gazikel;

public interface Subject {

    /**
     * 添加一个股民
     */
    void addInvestor(Investor investor);


    /**
     * 移除一个股民
     */
    void removeInvestor(Investor investor);

    /**
     * 通知所有的股民
     */
    void notifyInvestors();
}

Investor1实现Investor接口

package com.gazikel;

public class Investor1 implements Investor {

    private float range;

    @Override
    public void update(float range) {
        this.range = range;
        display();
    }

    public void display() {
        if (this.range > 0) {
            // 上涨消息
            System.out.println("买股票");
        } else if(this.range < 0) {
            // 下降消息
            System.out.println("大哭一场");
        }
    }
}

Stock实现Subject接口

package com.gazikel;

public class Investor1 implements Investor {

    private float range;

    @Override
    public void update(float range) {
        this.range = range;
        display();
    }

    public void display() {
        if (this.range > 0) {
            // 上涨消息
            System.out.println("买股票");
        } else if(this.range < 0) {
            // 下降消息
            System.out.println("大哭一场");
        }
    }
}

Client

package com.gazikel;

public class Client {

    public static void main(String[] args) {
        Investor investor1 = new Investor1();
        Stock stock = new Stock();
        // 添加股民
        stock.addInvestor(investor1);

        // 上涨不足5%，不会通知股民
        stock.setData(0.03f);
        System.out.println("------------------------");

        // 上涨超过5%，通知股民
        stock.setData(0.06f);
        System.out.println("------------------------");

        // 下降超过5%，通知股民
        stock.setData(-0.07f);
        System.out.println("------------------------");


    }
}

C++

#include<iostream>
#include<list>
using namespace std;

class Investor {
public:
	virtual void update(double range) = 0;
};

class Investor1 :public Investor {
private:
	double range;
public:
	void update(double range) {
		this->range = range;
		display();
	}
	void display() {
		if (this->range > 0) {
			cout << "买股票" << endl;
		}
		else if (this->range < 0) {
			cout << "大哭一场" << endl;
		}
	}
};

class Subject {
public:
	virtual void AddInvestor(Investor* investor) = 0;
	virtual void NotifyInvestors() = 0;
};

class Stock :public Subject {
private:
	double range;
	list<Investor*> investors;
public:
	void SetData(double range) {
		this->range = range;
		if (range > 0) {
			cout << "股票价格上涨了" << endl;
		}
		else if (this->range < 0) {
			cout << "股票价格下降了" << endl;
		}
		else {
			cout << "股票价格保持平稳" << endl;
		}
		if (this->range >= 0.05 || this->range <= -0.05) {
			NotifyInvestors();
		}
	}

	void AddInvestor(Investor *investor) {
		investors.push_back(investor);
	}

	void NotifyInvestors() {
		list<Investor*>::iterator it;
		for (it = investors.begin(); it != investors.end(); it++) {

			(*it)->update(this->range);

		}
	}
};

int main() {
	Investor* investor1 = new Investor1();

	Stock* stock = new Stock();

	// 添加股民
	stock->AddInvestor(investor1);

	// 上涨不足5%，不会通知股民
	stock->SetData(0.03);
	cout << "-------------------------------" << endl;

	// 上涨超过5%，通知股民
	stock->SetData(0.06f);
	cout << "-------------------------------" << endl;

	// 下降超过5%，通知股民
	stock->SetData(-0.07f);
	cout << "-------------------------------" << endl;
}