'' 的构造函数必须显式初始化引用成员 ''

Constructor for #39;#39; must explicitly initialize the reference member #39;#39;( 的构造函数必须显式初始化引用成员 )

问题描述

我有这门课

class CamFeed {
public:
    // constructor
    CamFeed(ofVideoGrabber &cam); 
    ofVideoGrabber &cam;

};

还有这个构造函数:

CamFeed::CamFeed(ofVideoGrabber &cam) {
    this->cam = cam;
}

我在构造函数上收到此错误:'' 的构造函数必须显式初始化引用成员 ''

I get this error on the constructor: Constructor for '' must explicitly initialize the reference member ''

有什么好的方法可以解决这个问题?

What is a good way to get around this?

推荐答案

需要使用构造函数初始化列表:

You need to use the constructor initializer list:

CamFeed::CamFeed(ofVideoGrabber& cam) : cam(cam) {}

这是因为引用必须引用某些东西，因此不能默认构造.进入构造函数体后，所有数据成员都已初始化.您的 this->cam = cam; 行实际上是一个赋值，将 cam 引用的值分配给任何 this->cam> 指的是.

This is because references must refer to something and therefore cannot be default constructed. Once you are in the constructor body, all your data members have been initialized. Your this->cam = cam; line would really be an assignment, assigning the value referred to by cam to whatever this->cam refers to.

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