c++ - 如何在不重复代码的情况下在子类中获取相同的方法代码？

Question

我有以下代码:

#include <exception>

class Exception : public std::exception {
private:
    const char* MESSAGE = "Exception"

public:
    inline virtual const char* what() const throw() {
        return this->MESSAGE;
    }
};

class ShoulderROMException : public Exception {
private:
    typedef Exception super;
    const char* MESSAGE = "ShoulderROM exception";

protected:
    static const int MAX_MESSAGE_LENGTH = 200;
    mutable char composedMessage[ShoulderROMException::MAX_MESSAGE_LENGTH];

public:
    virtual const char* what() const throw() {
        strcpy(this->composedMessage, super::what());
        strcat(this->composedMessage, " -> ");
        strcat(this->composedMessage, this->MESSAGE);
        return this->composedMessage;
    }
};

class KinectInitFailedException : public ShoulderROMException {
private:
    typedef ShoulderROMException super;
    const char* MESSAGE = "Kinect initialization failed."

public:
    virtual const char* what() const throw() {
        strcpy(this->composedMessage, super::what());
        strcat(this->composedMessage, " -> ");
        strcat(this->composedMessage, this->MESSAGE);
        return this->composedMessage;
    }
};

这会生成如下所示的日志条目: 异常 -> ShoulderROM 异常 -> Kinect 初始化失败。 这正是我想要的，但我想避免明显的代码重复并且似乎无法找到一种(优雅的)方法来做到这一点。

如果有人能在这里帮助我，那就太好了。 :)

最好的问候， 星际宝贝

Answer 1

通过普通类实现。我会像这样重写你的代码:

class Exception : public std::exception {
    static const char* MESSAGE = "Exception"
    static const int MAX_MESSAGE_LENGTH = 200;
    mutable char composedMessage[MAX_MESSAGE_LENGTH];

public:
    virtual const char* name() const throw() {
        return MESSAGE;
    }

    virtual const char* what() const throw() {
        strcpy(this->composedMessage, name());
        strcat(this->composedMessage, " -> ");
        strcat(this->composedMessage, this->MESSAGE);
        return this->composedMessage;
    }
};

class ShoulderROMException : public Exception {
    static const char* MESSAGE = "ShoulderROM exception";
public:    
    virtual const char* name() const throw() {
        return MESSAGE;
    }
};

class KinectInitFailedException : public ShoulderROMException {
    static const char* MESSAGE = "Kinect initialization failed."
public:
    virtual const char* name() const throw() {
        return MESSAGE;
    }
};

如果您不希望在 Exception 类中有太多实现，请添加另一个 ShoulderROMException 和 KinectInitFailedException 都将继承的类。

您的代码还有其他问题:MESSAGE 成员应该是static，并且您处理字符串的方式不是C++ish。我还要补充一点，内联虚函数没有任何意义。