C++ OStream繼承和機械手

Question

我有一個類從ostream繼承，但操縱器無法編譯。例如：

QLogger &logger = QLogger::getInstance(); 

logger << hex << 10 << endl; 

抱怨約logger << hex。如果我將記錄器投到ostream它會起作用，但這是相當不利的。

如何擴展我的班級，使其具有操作員的行爲ostream？

感謝，

肯尼

class LIBEXPORT QLogger: public std::ostream 
{ 
    friend class boost::thread_specific_ptr<QLogger>; 

    friend class QLoggerFunnel; 

public: 

    // Priority for message filtering. 
    // 
    // DEBUG Detailed information that may be useful during development or troubleshooting. 
    // NORMAL Message will be useful during normal operation. 
    // WARNING Message indicates an unhealthy condition but the system should continue to operate. 
    // FAULT Message indicates a critical error. The system may not operate normally. 
    enum Priority 
    { 
     DEBUG, NORMAL, WARNING, FAULT 
    }; 

    // DEPRECATED: Defined for backward compatibility. 
    static const Priority LOW = NORMAL; 

    static const Priority HIGH = WARNING; 

    static const Priority URGENT = FAULT; 

    // Returns a reference to the global instance. 
    static QLogger& getInstance(); 

    // DEPRECATED: Use instead: QLogger::instance() << "Example message." << std::endl 
    static AWI_DEPRECATED QLogger& stream(QLogger::Priority priority = NORMAL); 

    QLogger &operator<<(Priority p); 

    // Messages with a priority below the threshold are discarded. 
    void setThreshold(Priority priority); 

    Priority getThreshold(void) const; 

    // Set the priority of messages. 
    void setPriority(Priority priority); 

    Priority getPriority(void) const; 

protected: 

    static void handleThreadExit(QLogger *logger); 

    QLogger(); 

    QLogger(const QLogger&); 

    virtual ~QLogger(); 

    QLogger& operator=(const QLogger&); 

    void write(std::ostream &destination); 

    void synchronize(void); 

    // Prepends information to each line of its associated output stream. 
    class StampBuffer: public std::stringbuf 
    { 
     public: 

      StampBuffer(); 

      virtual ~StampBuffer(); 

      // String to be displayed before each line. 
      void setPreamble(const char *p); 

      virtual int sync(); 

      void write(std::ostream &destination); 

     protected: 

      boost::mutex _mutex; 

      std::stringstream _stream1; 

      std::stringstream _stream2; 

      // Active stream being written to. 
      std::stringstream *_write; 

      std::stringstream *_read; 

      const char *_preamble; 
    }; 

    class NullBuffer: public std::stringbuf 
    { 
     public: 

      NullBuffer(); 

      virtual ~NullBuffer(); 

      virtual int overflow(int c) 
      { 
       return (c); 
      } 
    }; 

    StampBuffer _buffer; 

    NullBuffer _null_buffer; 

    Priority _threshold; 

    Priority _priority; 
}; 

Answer 1

如果您實現一個成員函數，則繼承了相同功能的重載重載決策不考慮。如果您將自定義的重載更改爲好友全局函數而不是成員，則應該可以正常工作。演員強制編譯從ostream中定義的那些中選擇operator<<()。

函數指針的特殊重載是不需要的。