Question

How can I define an array as a member of class while its size determined somewhere else and actually it is passed to the constructor.

More detail:
There is an array of integer numbers and is defined a public member in class.

class foo {
  public:
    int *arr[];
    int s;
};

However the size of array is passed in the constructor.

foo::foo()
        : s (array_size)
{
}

What is the correct syntax of doing such thing?

Answer 1

The correct way of doing this is to use the STL and std::vector< int > for such tasks. The following is a rough outline that may work for you:

#include <vector>

...

class foo
{
    public:
        std::vector< int > arr_;

        ...

        foo(const int* numbers, int numberCount)
        : arr_(numbers, numbers+numberCount)
        {
        }

        ...

        int size() const
        {
            return arr_.size();
        }

        ...

        int& operator [] (int index)
        {
           return arr_.at(index);
        }
};

Further information on vectors can be found here. Further suggestions:

• don’t make your instance variables public if there is no compelling reason to do so.
• name instance variables somehow special (for example by appending a _).
• many people dislike classes that are named all lowercase.