c++ - 创建自己的vector Class，错误很多

Question

我是 C++ 的新手，使用它创建类，尤其是使用模板类。我收到了很多错误消息，但我不确定如何解决它们，希望这里有人能提供帮助，在此先感谢。

类:

template <class T> class Vector {
    public:
        typedef T* iterator;
        Vector();
        iterator begin();
        iterator end();
        int size();
        iterator insert(iterator position, const T& item);
        void alloc_new();

    private:
        T items;
        int used;      
};

template <class T> Vector::Vector() { 
    items = [1000];
    used = 0;
}

template <class T> iterator Vector::begin() {
   return items; 
}

template <class T> iterator Vector::end(){
    return items + used;
}

template <class T> int Vector::size() {
    return used;
}

template <class T> iterator Vector::insert(iterator position, const T& item){

    if (used+1 > items){
        alloc_new();}  

    items[position] = item;
    used =+ 1;

}

template <class T> void Vector::alloc_new(){
        items = used*2;
        T tmp[] = items;

        for (int i = 0; i < used; i++){
            tmp[i] = items[i];
        } 
        delete items;
        items = tmp;
    }

错误信息:

main.cpp:67: error: `template class Vector' used without template parametersmain.cpp:67: error: ISO C++ forbids declaration of `Vector' with no typemain.cpp:67: error: declaration of template `template int Vector()'main.cpp:52: error: conflicts with previous declaration `template class Vector'main.cpp:52: error: previous non-function declaration `template class Vector'main.cpp:67: error: conflicts with function declaration `template int Vector()'main.cpp: In function `int Vector()':main.cpp:68: error: `items' undeclared (first use this function)main.cpp:68: error: (Each undeclared identifier is reported only once for each function it appears in.)main.cpp:68: error: expected primary-expression before '[' tokenmain.cpp:69: error: `used' undeclared (first use this function)main.cpp: At global scope:main.cpp:72: error: expected constructor, destructor, or type conversion before "Vector"main.cpp:72: error: expected `;' before "Vector"main.cpp:76: error: expected constructor, destructor, or type conversion before "Vector"main.cpp:76: error: expected `;' before "Vector"main.cpp:80: error: `template class Vector' used without template parametersmain.cpp: In function `int size()':main.cpp:81: error: `used' undeclared (first use this function)main.cpp: At global scope:main.cpp:84: error: expected constructor, destructor, or type conversion before "Vector"main.cpp:84: error: expected `;' before "Vector"main.cpp:94: error: `template class Vector' used without template parametersmain.cpp: In function `void alloc_new()':main.cpp:95: error: `items' undeclared (first use this function)main.cpp:95: error: `used' undeclared (first use this function)

Answer 1

您需要指定模板参数。例如:

template <class T> Vector<T>::Vector() { 
    items = [1000];  // note, this is also invalid syntax
    used = 0;
}