Question

Hi I am pretty new to C++ I’m a lot more used to Java. But what I want to do is create just an empty arrayList that can be used by all of my other functions.

In my .h file I created a new class which has 2 structs within it and about 6 methods. Each of these methods uses arrayLists of the struct objects, but I don’t want to have to pass in the arrayLists as parameters. What I am trying to do is similar to in Java when you create a field in a class.

The problem is when I declare the arrayList like this in my .h file…

structObject * myArrayList = new structObject[0];
int ARRAY_SIZE = arrayList.size;

I get a bunch of errors including new cannot be declared in a constant.

Where should I be trying to declare my empty arraylist?
Is this even permissible in C++?

Answer 1

You are trying to put a definition in a header file. That is a not allowed. You can only put declarations in a header file.

declaration in the header:

structObject* myArrayList;
#define ARRAY_SIZE 100

definition in a source file:

myArrayList = new structObject[ARRAY_SIZE];

However, global variables are almost always a bad idea. I would find a way to pass the array as an argument to the necessary functions. You should also look into the Standard Template Library and look at different containers.

one option:

std::vector<structObject> myArrayList;

That can be put in a header file, and the constructor will do necessary initialization.