My c++ function is destroying variables when it shouldn't be

Question

The purpose of this function is to take a struct, and enlarge the array by 1. It does this by copying the array to a temporary array, deleting and recreating the original with a larger size. My problem is that when I run the function, all of my values within the struct become '-17891602'. Correct me if I'm wrong, but I believe that this is the value that shows when the variable has been deleted? I can't figure out the problem. But here's the definition.

void Array::addValueStruct(int id, int size, int type, int compareValue, StoredData temp[])
{
    //struct
    StoredData* tempStruct = new StoredData [arrSize+1];
    for (int i=0;i<arrSize;i++)
    {
        tempStruct[i] = temp[i];
    }

    arrSize = arrSize + 1;

    delete [] temp;

    temp = tempStruct;

    temp[arrSize-1].id = id;
    temp[arrSize-1].size = size;
    temp[arrSize-1].type = type;
    temp[arrSize-1].compareValue = compareValue;
}

Also, not sure if this is helpful, but the function call.

test.addValueStruct(5,5,5,5,testData);

UPDATE: Problem solved!

Answer 1

The issue is that the array pointer is passed into the function by value. This means that when you reassign it to point to a different array, this change does not propagate back to the caller.

You need to pass it either by pointer or by reference.

Answer 2

You are passing temp by value. Therefore, addValueStruct gets its own copy and changes made to it are not visible outside that function scope.

Answer 3

The problem probably is this line here:

temp = tempStruct;

Here you only changing the local copy of the temp variable. If you want to modify the variable used for the call you have to pass it by reference.