如何向基类注册派生类成员函数指针 [英] How to register a derived class member function pointer with a base class

问题描述

与虚拟成员函数相反，我需要一个解决方案，其中在每个级别类派生中实现的函数可以注册以供基类稍后调用。 （不仅仅是最派生的实现）

As opposed to virtual member functions, I need a solution where a function implemented at each level class derivation can be registered for later call by the base class. ( Not just the most derived implementation)

为了做到这一点，我想为派生类提供一种机制来向基类注册它们的函数，类构造函数。

To do this, I was thinking on providing a mechanism for derived classes to register their function with the base class such as during the derived class constructor.

我有成员函数指针参数的麻烦。我认为Derived派生自Base，这个指针应该被自动转换。

I'm having trouble with the member function pointer argument though. I was thinking that Derived is derived from Base, the this pointer should be automatically casted.

这可以接近我想要的，或者我需要使用静态成员函数， void * 和 static_cast ？

class Base
{
protected:
    typedef void (Base::*PrepFn)( int n );
    void registerPrepFn( PrepFn fn ) {};
}

class Derived : public Base
{
    Derived() {
        registerPrepFn( &Derived::derivedPrepFn );
    };

    void derivedPrepFn( int n ) {};

}

编译器错误：

error: no matching function for call to 'Derived::registerPrepFn(void (Derived::*)(int))'
note: candidates are:                 'void Base::registerPrepFn(void (Base::*)(int))'

推荐答案

如果所有你需要的是跳动的错误信息，然后强制执行：

If all you need is beating the error message, then casting will do:

class Derived : public Base
{
    Derived() {
        registerPrepFn( static_cast<PrepFn>(&Derived::derivedPrepFn) );
    };

    void derivedPrepFn( int n ) {};

}

使用 * p （，只要它实际指向一个派生）：（p-> *已注册）（0）

请参阅 http://ideone.com/BB9oy 以获取实用示例。

See http://ideone.com/BB9oy for a working example.

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