Why do i get "invalid use of non-static data member" error when i try to create an array inside class?

Question

I created an array with the length of x but I get the error

invalid use of non-static data member Test::x.

I tried to replace int newArray[x]; with int newArray = new int[x]; but still didn't work out. When I declared the newArray[x] in the constructor or put static const before int x = 10, the code run successfully. Why is that?

#include <iostream>
#include <vector>
using namespace std;

class Test
{
private:
    int x = 10;
    int newArray[x];
public:
    Test();
    ~Test();
};
int main()
{

    return 0;
}

You may want to read this : https://stackoverflow.com/questions/18996258/array-initialization-use-const-variable-in-c — Spinkoo, Mar 25 '19 at 11:19
The size of arrays must be known at compile-time. Use `vector` if that cannot happen. — M.M, Mar 25 '19 at 11:21

Aykhan Hagverdili · Accepted Answer · 2019-03-25T11:44:38.027

1

int newArray[x]; won't work because size of a static array needs to be known at compile time. Adding static constexpr to the declaration of x makes it a compile time constant and that's why the code compiles.
int newArray = new int[x]; won't work either, because operator new returns a pointer, which cannot be assigned to an integer. Having said that, consider using std::vector instead.

edited Mar 25 '19 at 11:44

answered Mar 25 '19 at 11:23

Aykhan Hagverdili

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@Downvoter Can anyone suggest improvements or corrections to this? – Aykhan Hagverdili Mar 25 '19 at 11:48

Why do i get "invalid use of non-static data member" error when i try to create an array inside class?

1 Answers1