What's the syntax for creating an array of pointers to another class?

Question

If I have a class with a private variable that's supposed to hold an array of pointers to another class, is the following syntax correct?

class MyClass
{
    private:
        int arraySize;
        SomeOtherClass* classPtr[];
}

Later, when I want to dynamically allocate memory for this array in a function in MyClass that accepts an ifstream, reads from a file, and fills the array, would I do it like this?

void createArray(std::ifstream& fin)
{
    //the first int is the array size
    fin >> arraySize;
    string tempString; //the file is formatted string int string int etc.
    int tempInt;

    classPtr[arraySize];

    for(int i = 0; i < arraySize; i++)
    {
        fin >> tempString;
        fin >> tempInt;
        //assume the constructor is defined
        classPtr[i] = new SomeOtherClass(tempString, tempInt);
    }

Thanks for your time in advance.

Answer 1

That's incorrect. You cannot yet use variable length arrays in C++

That should be

SomeOtherClass** classPtr;

And in createArray()

...
classPtr = new SomeOtherClass*[arraySize];
...

And yes, forget everything I said and use std::vector

Answer 2

Arrays must have a static size at compile time, but in your case you don't know the size until you read it from the stream at runtime. For a dynamically sized array, you should use a vector instead:

std::vector<SomeOtherClass*> classPtr;

Then in your code below:

classPtr.reserve(arraySize);
.....
classPtr.push_back(new SomeOtherClass(...));

This being said, using raw pointers in a vector is not advised and should be done with care. Read this answer to learn more about it and whether its right for you. More likely than not, you just want a vector of your objects:

std::vector<SomeOtherClass> vec;
.....
vec.push_back(SomeOtherClass(...));

When using a vector of objects you should be sure to think about the move/copy semantics of your object and make sure that its right for your use case.