模板函数覆盖std :: vector :: assign

Question

I am writing a C++ class which contains a member vector . I would like to override the vector methods so that MyVector can be used like a std::vector . However, the assign method keeps throwing a compile error:

#include <vector>

template<class T>
struct MyVector {
    typedef std::vector<T> vector_type;

    vector_type my_vector;

    template<class It>
    void assign(It first, It last)
    {
        my_vector.assign<It>(first, last);
    }
};

The error:

myvector.cpp: In member function ‘void MyVector<T>::assign(It, It)’:
myvector.cpp:12:22: error: expected primary-expression before ‘>’ token
my_vector.assign<It>(first, last);

This code compiles without the outer template T . In other words, by changing the vector type to:

typedef std::vector<int> vector_type;

will make the compile error go away, but it doesn't serve my needs though.

The code is compiled on Linux (Ubuntu 18) with gcc version 7.4.0:

gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)

Answer 1

You need to use the keyword template to tell that assign is a template.

my_vector.template assign<It>(first, last);
//        ^^^^^^^^

BTW: The template parameter of std::vector::assign could be deduced automatically, so you don't need to specify the template argument explicitly in fact. So just

my_vector.assign(first, last);