Question

考虑这个课程：

class baseController {

    /* Action handler array*/

std::unordered_map<unsigned int, baseController*> actionControllers;

protected:

    /**
     *  Initialization. Can be optionally implemented.
     */
    virtual void init() {

    }

    /**
     * This must be implemented by subclasses in order to implement their action
     * management
     */
    virtual void handleAction(ACTION action, baseController *source) = 0;

    /**
     * Adds an action controller for an action. The actions specified in the
     * action array won't be passed to handleAction. If a controller is already
     * present for a certain action, it will be replaced.
     */
    void attachActionController(unsigned int *actionArr, int len,
            baseController *controller);

    /**
     *
     *  checks if any controller is attached to an action
     *
     */
    bool checkIfActionIsHandled(unsigned int action);

    /**
     *
     *  removes actions from the action-controller filter.
     *  returns false if the action was not in the filter.
     *  Controllers are not destoyed.
     */
    bool removeActionFromHandler(unsigned int action);

public:

    baseController();

    void doAction(ACTION action, baseController *source);

};

}

和这个子类

class testController : public baseController{

    testController tc;

protected:

    void init(){
        cout << "init of test";
    }



    void handleAction(ACTION action, baseController *source){

        cout << "nothing\n";

    }

};

编译器在成员

的子类上出错

testController tc;

..说

error: field ‘tc’ has incomplete type

但是，如果我删除它并且我实例化它的工作...有没有办法避免这个错误???它看起来很奇怪....

Answer 1

one day someone asked me why a class can't contain an instance of itself and i said;
  one day someone asked me why a class can't contain an instance of itself and i said;
    one day someone asked me why a class can't contain an instance of itself and i said;
      ...

使用间接。一个（智能）指针或对testController的引用，而不是testController。

Answer 2

您的代码正在尝试将testController的整个实例嵌入其中，这是不可能的。相反，你想要一个参考：

testController &tc;

或指针

testController *tc;

Answer 3

它不会编译，因为你声明一个成员变量'tc'是它自己的一个实例。你没有在子类中使用tc;你的意图是什么？

Answer 4

您无法在该类本身内创建该类的对象。你打算做的是保持指向类的指针。在这种情况下，您应该将其用作testController* BTW，为什么要这样做？这对我来说有点奇怪。

Answer 5

（派对有点晚了，但是......）

也许gotch4打算输入这样的东西？

class testController : public baseController
{
public:
    testController tc();  // <- () makes this a c'tor, not a member variable

    // ( ... snip ... )
};

c ++虚拟类，子类和自引用

5 个答案: