在类中定义一个const静态对象变量 [英] Define a const static object variable inside the class

问题描述

我需要在类定义内创建一个静态对象。这是可能在Java，但在C + +我得到一个错误：

I need to create a static object inside a class definition. It is possible in Java, but in C++ I get an error:

../PlaceID.h:9:43: error: invalid use of incomplete type ‘class
PlaceID’ ../PlaceID.h:3:7: error: forward declaration of ‘class
PlaceID’ ../PlaceID.h:9:43: error: invalid in-class initialization of static data 

我的类看起来像这样：

#include <string>

class PlaceID {

public:

    inline PlaceID(const std::string placeName):mPlaceName(placeName) {}

    const static PlaceID OUTSIDE = PlaceID("");

private:
    std::string mPlaceName;
};

是否可以在此类中创建一个类的对象？

Is it possible to make an object of a class inside this class? What are prerequisites that it must hold?

推荐答案

您不能定义成员变量，因为类尚未完全定义。你必须这样做：

You can't define the member variable because the class isn't fully defined yet. You have to do like this instead:

class PlaceID {

public:

    inline PlaceID(const std::string placeName):mPlaceName(placeName) {}

    const static PlaceID OUTSIDE;

private:
    std::string mPlaceName;
};

const PlaceID PlaceID::OUTSIDE = PlaceID("");

这篇关于在类中定义一个const静态对象变量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！