c++ - std::ostream& operator<<(std::ostream&, const T&) 未被覆盖

Question

偶尔我会写一个类(T 说)并尝试覆盖 std::ostream& operator<<(std::ostream&, const T&) 但它不适用于某些类。这是一个(简化的)类的示例，它对我不起作用。

class ConfigFile {
public:
    explicit ConfigFile(const std::string& filename);
    virtual ~ConfigFile();

    bool saveToDisk() const;
    bool loadFromDisk();

    std::string getSetting(const std::string& setting, const std::string& section="Misc") const;
    void setSetting(std::string value, const std::string& name, const std::string& section ="Misc", bool updateDisk = false);

    inline const SettingSectionMap& getSettingMap() const {
         return mSettingMap;
    }

private:
    std::string         mSettingFileName;
    SettingSectionMap       mSettingMap;

#if  defined(_DEBUG) || defined(DEBUG)
public:
    friend std::ostream& operator<<(std::ostream& output, const ConfigFile& c) {
        output << “Output the settings map here”;
        return output;
    }
#endif
}

我很确定 explicit 关键字会阻止转换构造函数的情况，但它确实像它一样，因为当我做类似的事情时

std::cout << config_ << std::endl;

它的输出类似于:0x100588140。但是后来我在另一个类(class)做了同样的事情，就像下面的类(class)一样，一切正常。

class Stats {
    Stats() {};

#if  defined(_DEBUG) || defined(DEBUG)
    friend std::ostream& operator<<(std::ostream& output, const Stats& p) {
        output << "FPS Stats: " << p.lastFPS_ << ", " << p.avgFPS_ << ", " << p.bestFPS_ << ", " << p.worstFPS_ << " (Last/Average/Best/Worst)";
        return output;
    };
#endif
}; 

感谢您的帮助。

编辑:为了解决这个问题，我现在将以下内容添加到我的所有类(class)中:

#if  defined(_DEBUG) || defined(DEBUG)
public:
    friend std::ostream& operator<<(std::ostream& output, const ConfigFile& c);
    friend std::ostream& operator<<(std::ostream& output, ConfigFile* c) {
        output << *c;
        return output;
}
#endif

Answer 1

尝试将签名更改为 const 指针:

std::ostream& operator<<(std::ostream& output, const ConfigFile* c);