子类上的 C++ 模板父类构造函数

Question

我有这个

template<class PayloadType>
    class Event {
    protected:
        PayloadType payload;
    public:
        Event(PayloadType payload);
    };

这是定义:

template<class PayloadType>
Event<PayloadType>::Event(PayloadType payload) {
    this->payload = payload;
}

还有这个:

class SimplePayload {
protected:
    int number;
public:
    SimplePayload(int number) : number(number) { }
    int getNumber() { return number; };
};

template<class PayloadType>
class SimpleEvent : public Event<PayloadType> {
protected:
    PayloadType payload;
public:
    SimpleEvent(PayloadType payload) : Event<PayloadType>(payload) { }
};

尝试使用它:

SimplePayload simplePayload;
SimpleEvent<SimplePayload> *simpleEvent = dynamic_cast<SimpleEvent<SimplePayload>*>(new Event<SimplePayload>(simplePayload));

我收到这个错误:

error: member initializer 'Event' does not name a non-static data member or base class

如何正确构造对象？

Answer 1

您需要指定模板参数:

template<class PayloadType>
class SimpleEvent : public Event<PayloadType> {
protected:
    PayloadType payload;
public:
    SimpleEvent(PayloadType payload) : Event<PayloadType>(payload) { }
                                            ~~~~~~~~~~~~~
};

编辑

对于链接错误，尝试将定义移动到头文件。

参见 Why can templates only be implemented in the header file?