C++ expression must have class type with class template

Question

I am trying to an Array class with a template and I have a problem.

List.h:

template<class T>
class Array
{
private:
    T** List;
    int Capacity; 
    int Size; 
public:
    Array(); 
    ~Array();
    Array(int capacity);
    Array(const Array<T>& otherArray); 
    int GetSize();
    int GetCapacity();
};

And the List.cpp file looks like

#include "List.h"
#include <iostream>
#include <stdio.h>

template<class T>
Array<T>::Array()
{
    printf("Default constructor called!\n");
    Capacity = 0;
    Size = 0;
}

template<class T>
Array<T>::~Array()
{
    delete List;
    Capacity = 0;
    Size = 0;
}

template<class T>
int Array<T>::GetCapacity()
{
    return Capacity;
}

And the main :

int main()
{
    Array<char> A(); //Calling the default constructor
    std::cout << A.GetCapacity();
}

I am calling the default constructor but I don't get anything in the console. I think that I did something wrong with the constructor call or with the constructor declaration.

`ArrayA();` declares a function called `A` that returns a `Array` — 463035818_is_not_an_ai, May 05 '20 at 12:38
You don't get output in console because your program never ran. You got a compilation error. — Yksisarvinen, May 05 '20 at 12:38
@idclev463035818 then how am I supposed to call the default constructor? — , May 05 '20 at 12:41
get rid of the brackets: `Array A;` also AAA helps here: `auto A = Array;` — 463035818_is_not_an_ai, May 05 '20 at 12:42
@ValentinGrigorean, My unstated point is that Clang can give a perfectly comprehensible warning here. If a compiler error is giving you trouble on one compiler, try another. — chris, May 05 '20 at 12:43
@ValentinGrigorean Because without last `cout` you never use `A`. And the syntax that uses default constructor would be (simply) `Array A;` or (with uniform initialization) `Array A {};` or (slightly longer) `Array A = Array();` — Yksisarvinen, May 05 '20 at 12:43
@idclev463035818 I am getting unresolved external for ```Array A``` and type name is not allowed for ```auto A = Array``` — , May 05 '20 at 12:46
thats a problem then that is no present in the code you posted. Please provide a [mcve] — 463035818_is_not_an_ai, May 05 '20 at 12:47
did you maybe put the definitions for the template in a source file? — 463035818_is_not_an_ai, May 05 '20 at 12:48
Yes, you put your template definitions in a source file. Delete `List.cpp` put all the code in `List.h`. See [here](https://stackoverflow.com/questions/495021/why-can-templates-only-be-implemented-in-the-header-file) — john, May 05 '20 at 13:00
@idclev463035818 Thank you! The problem was because of the template definitions being in a different file — , May 05 '20 at 13:12

C++ expression must have class type with class template

0 Answers0