Question

Ok, So I’ve googled this problem and I have searched stack overflow but I can’t seem to find a good answer. So, I am asking the question on here that is particular to my problem. If it is an easy answer, please be nice, I am new to the language. Here is my problem:

I am trying to write a method for a C++ class that is overloading an operator. I want to return a copy of the instance modified but not the instance itself. For ease of example, I’ll use a BigInt class to demonstrate the problem that I am having.

If I had the following code:

const BigInt & operator+() const //returns a positive of the number
{
    BigInt returnValue = *this;  //this is where I THINK the problem is
    returnValue.makepositve();   //for examples sake
    return returnValue;
}

I get the error that the return value may have been created on the stack. I know that this means that I have to create the object on the heap and return the reference. But If I were to change the 3^rd line to something like:

BigInt & returnValue = *this;

I get an error telling me that the syntax is not right. I’m not really sure what to do, any help is much appreciated!

Answer 1

The problem is in your function signature. You really do have to return the entire object and not just a reference.

Your function will look like this

BigInt operator+() const //returns a positive of the number
{
    BigInt returnValue = *this;
    returnValue.makepositve();   //for examples sake
    return returnValue;
}