c++类调用的一个小问题
2024-09-02 05:49:49
先看这两段代码：
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
class Subject
{
public:
Subject(){}
virtual ~Subject(){}
virtual void attach(MyObserver *observer)=0;
virtual void detach(MyObserver *observer)=0;
virtual void stockUp()=0;
virtual void stockDown()=0;
};
class Stock:public Subject
{
public:
void attach(MyObserver *observer)
{
observers.push_back(observer);
}
void detach(MyObserver *observer)
{
vector<MyObserver*>::iterator observer_rm = find(observers.begin(), observers.end(), observer);
observers.erase(observer_rm);
}
void stockUp()
{
cout<<"股票上涨5%"<<endl;
vector <MyObserver *>::iterator iObserver = observers.begin();
while(iObserver != observers.end())
{
(*iObserver)->response1();
iObserver++;
}
}
void stockDown()
{
vector <MyObserver *>::iterator iObserver = observers.begin();
cout<<"股票下降5%"<<endl;
while(iObserver != observers.end())
{
(*iObserver)->response2();
iObserver++;
}
}
private:
vector<MyObserver*> observers;
};
class MyObserver
{
public:
virtual void response1() = 0;
virtual void response2() = 0;
}; class Investor:public MyObserver
{
public:
void response1(){
cout<<"股民买股票"<<endl;
}
void response2(){
cout<<"股民大哭一场"<<endl;
}
};
int main()
{
Stock subject;
Investor obs;
subject.attach(&obs);
subject.stockUp();
subject.stockDown();
}
c++代码片段一
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
class MyObserver
{
public:
virtual void response1() = 0;
virtual void response2() = 0;
}; class Investor:public MyObserver
{
public:
void response1(){
cout<<"股民买股票"<<endl;
}
void response2(){
cout<<"股民大哭一场"<<endl;
}
};
class Subject
{
public:
Subject(){}
virtual ~Subject(){}
virtual void attach(MyObserver *observer)=0;
virtual void detach(MyObserver *observer)=0;
virtual void stockUp()=0;
virtual void stockDown()=0;
};
class Stock:public Subject
{
public:
void attach(MyObserver *observer)
{
observers.push_back(observer);
}
void detach(MyObserver *observer)
{
vector<MyObserver*>::iterator observer_rm = find(observers.begin(), observers.end(), observer);
observers.erase(observer_rm);
}
void stockUp()
{
cout<<"股票上涨5%"<<endl;
vector <MyObserver *>::iterator iObserver = observers.begin();
while(iObserver != observers.end())
{
(*iObserver)->response1();
iObserver++;
}
}
void stockDown()
{
vector <MyObserver *>::iterator iObserver = observers.begin();
cout<<"股票下降5%"<<endl;
while(iObserver != observers.end())
{
(*iObserver)->response2();
iObserver++;
}
}
private:
vector<MyObserver*> observers;
};
int main()
{
Stock subject;
Investor obs;
subject.attach(&obs);
subject.stockUp();
subject.stockDown();
}
c++代码片段二
运行后：片段一运行错误，片段二运行成功
后来发现，在Subject中调用MyObserver时，类MyObserver应放在Subject之前，才能调用成功，也就是说在c++中如果想要调用某个类，应放在前面，或者如果不想管顺序，那就需要提前进行类的声明。
用java用习惯了，用c++有点陌生了。
最新文章
- openstack云5天资料
- php类的__get和__set方法
- @RequestMapping用法详解
- 【转】mysql触发器的实战（触发器执行失败，sql会回滚吗）
- 如何清除朗逸保养提示标志INSP
- C# 无边框窗体之窗体移动
- Hibernate常用配置文件详解
- Selenium2Library系列 keywords 之 _SelectElementKeywords 之 select_from_list(self, locator, *items)
- Android Shape画圆，矩形
- IntelliJ IDEA 14 注册码生成java代码（转）
- wap网页、微信内嵌网页在手机端页面窗口尺寸如何不缩放
- IBM RAD 快捷键
- 关于wordpress升级遇到的问题
- Mac vs code 快捷键
- win10的linux子系统安装及使用
- SpringBoot小新手。
- 搭建Vue.js环境，建立一个简单的Vue项目
- 【转】每天一个linux命令（10）：cat 命令
- 函数parseQuery用于解析url查询参数
- asp.net core + 前端H5 页面视频站制作尝试