C ++需要typename [duplicate]的函数指针向量

typedef int (*fptr)(Data); // Data is a template class (this is from within a generic class)
// listeners is of type vector<fptr>, and this function is a member function of class Event
Event& add(fptr func) {
    for (std::vector<fptr>::iterator iter = listeners.begin(); iter != listeners.end(); ++iter) {
        if (*iter == func)
            return *this;
    }
    listeners.push_back(func);
    return *this;
}

g++ -Wall  -g     -c /root/learncpp/EventHandler/main.cpp -o obj/Debug/main.o
In file included from /root/learncpp/EventHandler/main.cpp:3:
/root/learncpp/EventHandler/event.h: In member function 'Event<Data>& Event<Data>::add(int (*)(Data))':
/root/learncpp/EventHandler/event.h:11: error: expected ';' before 'iter'
/root/learncpp/EventHandler/event.h:11: error: 'iter' was not declared in this scope
/root/learncpp/EventHandler/event.h: In member function 'Event<Data>& Event<Data>::add(int (*)(Data)) [with Data = std::basic_string<char, std::char_traits<char>, std::allocator<char> >]':
/root/learncpp/EventHandler/main.cpp:18:   instantiated from here
/root/learncpp/EventHandler/event.h:11: error: dependent-name 'std::vector::iterator' is parsed as a non-type, but instantiation yields a type
/root/learncpp/EventHandler/event.h:11: note: say 'typename std::vector::iterator' if a type is meant
Process terminated with status 1 (0 minutes, 2 seconds)
3 errors, 0 warnings

for (typename std::vector<fptr>::iterator iter = listeners.begin(); iter != listeners.end(); ++iter) {

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