Copying data from one dynamic array to another

[Hengry]

I have to create a larger array doubled in size if the initial array is full, the copy all the elements of array over to the new array. After i created the new array, I insert data into the end of the array, increase the size by 1. I'm confused and was wondering if my code is correct.

  if(arraySize == arrayCapacity){
		arrayCapacity*=2;
		T* temp = new T[arrayCapacity];
		for(int index=0; index<arraySize; index++)
			temp[i] = *(array)[i];
		delete [] array;
		array = temp; // array is now the same as temp array
                delete [] temp; 
	}
	array[arraySize] = data;
	arraySize++;
	delete [] array;
	return true;

array, arraySize and arrayCapacity are initialized as:

	arrayCapacity = 3;
	arraySize = 0;
	array = new T[arrayCapacity];

[AbstractionAnon]

was wondering if my code is correct.

No.

Line 8 You're deleting the new array.

Line 12: Why are you deleting array there? You now have no memory allocated.

Why not use std::vector? It eliminates the need to manage memory yourself.

[Hengry]

I have to create a my very own vector class, therefore I can't use vector.

delete [] temp; // I was planning to delete the temp array after copying the elements over. 
delete [] array; // I had to impression that since I set array = temp there would be 
memory allocated at array.  

For line 7: array = temp; just to make sure, this will copy all the elements and and the new capacity of the temp array

Are arrays only dynamically allocated when I use
T* array= new int[arrayCapacity] once deleted with delete [] array I will have to use new to allocate it to the heap?

I guess my correction will be:

 if(arraySize == arrayCapacity){
		arrayCapacity*=2;
		T* temp = new T[arrayCapacity];
		for(int index=0; index<arraySize; index++)
			temp[i] = *(array)[i];
		array = temp; 
                delete [] temp; 
	}
	array[arraySize] = data;
	arraySize++;
	delete [] array;
	return true;

[keskiverto]

Still off.

First, lines 9-12 have nothing to do with expansion.

On line 5 you have *( ). Why?

On line 6 you forget (leak) the original array.

On line 7 you delete the new array, into which both temp and array point to.


PS. Does your class have custom copy constructor, copy assingment, and destructor? It probably must have.

[Hengry]

Would this be right? After looking through your suggestions.

 if(arraySize == arrayCapacity){
		arrayCapacity*=2;
		T* temp = new T[arrayCapacity];
		for(int index=0; index<arraySize; index++)
			temp[i] = array[i] // copies elements in array to temp
		array = temp;
                delete [] array; //deallocates the array
	}

I do have a destructor, but i didn't make a function for copy

[keskiverto]

Before this code the array points to memory block A.
On line 3 temp starts to point to memory block B.
The loop copies (correctly) elements from A to B.

On line 6 the array starts to point to B. Nobody points to A.
array points to B.
temp points to B.
On line 7 you do delete B.
array now points to already deallocated memory.
Nobody did deallocate A.

You have to take a different approach. Hint: T* temp = array;


You will have to either prevent copying or implement copy constructor and copy assignment.