How to implement template inner class function (C++)

Question

considering the example below:

template <typename T>
class Vector {
    T* data;
public:
    class Iterator {
        T* i;
    public:
        Iterator& operator++();
    };
};

if I want to implement the 'operator++' function, it makes sence I'ld write like this:

template <typename T>
Vector<T>::Iterator& Vector<T>::Iterator::operator++() {
    i++;
    return *this;
}

but then I'm getting those error lines:

error C2143: syntax error : missing ';' before '&'
error C2065: 'T' : undeclared identifier
error C2923: 'Vector' : 'T' is not a valid template type argument for parameter 'T'

Why does it happen? and what should I do to solve this?

Thanks a lot.

`template typename Vector::Iterator& Vector::Iterator::operator++() {` — Piotr Skotnicki, Jun 10 '15 at 09:20

score 1 · Answer 1 · edited May 23 '17 at 12:15

1

The compiler doesn't know that the member Iterator of Vector is necessarily a type, so you need to tell it with the typename keyword:

template <typename T>
typename Vector<T>::Iterator& Vector<T>::Iterator::operator++() {
//here^
    i++;
    return *this;
}

See this question for more details about typename.

edited May 23 '17 at 12:15

Community

1
1

answered Jun 10 '15 at 09:27

TartanLlama

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Ahhaha, «the smart thought goes to heads in the same time» I even linked the same question *(the answer, though)*. Okay, removing. – Hi-Angel Jun 10 '15 at 09:31
Thank you vey much!! I'll see it. – Yoni Weisberg Jun 10 '15 at 09:32
1

or `auto Vector::Iterator::operator++() -> Iterator&` in C++11 – Piotr Skotnicki Jun 10 '15 at 09:33

How to implement template inner class function (C++)

1 Answers1