How should I declare a member variable in a function that will be visible to the rest of the class (but not global)?

Question

My code looks something like this:

namespace N {
    class C {
    public:
        void function1() {
            // code
        }
        
        void function2() {
            // code
        }

        C(int length) {
            int array[length] = {}
        }
    }
}

How should I make the array visible to other parts of the class (e.g. function1 and function2) without making it a global variable? I can't declare the variable in the private part of the class because I need to set the length according to the constructor input while the variable is being declared.

can you explain the code/problem a bit more? i dont think i got your question — Shreeyash Shrestha, Jun 30 '23 at 02:46
So I want to declare an array in a constructor, but I want it to be visible to the other functions of the class. If I just declare it normally that variable will only be visible to the constructor function, and I don't want it to be a global variable either. — stickynotememo, Jun 30 '23 at 02:48
*Why the downvote?* I guess because of not enough research was done and the missing semicolons. — 273K, Jun 30 '23 at 02:50
I did googling. Also the semicolons are because I haven't done anything other than JS in several months and my IDE didn't say anything. — stickynotememo, Jun 30 '23 at 02:51

score 0 · Answer 1 · answered Jun 30 '23 at 02:48

Use dynamic memory allocation and store the array as a pointer.

namespace N {
    class C {
    public:
        void function1() {
            // code
        }
        
        void function2() {
            // code
        }

        C(int length) 
           : array(new int[length]) {}
        ~C() {
            delete [] array;
        }
    private:
        int* array;
    }
}

Alternatively, use std::vector instead...

#include <vector>
namespace N {
    class C {
    public:
        void function1() {
            // code
        }
        
        void function2() {
            // code
        }

        C(int length) 
           : array(length) {}

    private:
        std::vector<int> array;
    }
}

The first code is no-go, and it vialoates the rule of 0-3. – 273K Jun 30 '23 at 02:53 — 273K, Jun 30 '23 at 02:53
@273K I sense you're fairly liberal with your downvotes. – stickynotememo Jun 30 '23 at 02:59 — stickynotememo, Jun 30 '23 at 02:59

score 0 · Answer 2 · answered Jun 30 '23 at 02:48

0

Any C++ book would teach you:

class C {
public:
    C(int length) : array(length) {
    }
private:
    std::vector<int> array;
};

answered Jun 30 '23 at 02:48

273K

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Can you explain in more detail how this works? – stickynotememo Jun 30 '23 at 02:53
`namespace std has no member vector` :) – stickynotememo Jun 30 '23 at 03:08

How should I declare a member variable in a function that will be visible to the rest of the class (but not global)?

2 Answers2