Operator Overloading problem

Hello. I have a class that holds a set of data. Each piece of data is represented by another class. I wanted to overload the += operator for the dataset class, but it appears gcc mistakes my effort as trying to use the binary + operator. Below is the related function.

Code:

---

CDataFile *CDataFile::operator+=(CData *wave) {
CNode *node;
        node=new CNode((void *)wave);
        WaveList.AddTail(node);
        return this;
}

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WaveList is a member object of CDataFile. Below, datafile is an instance of CDataFile and currwave one of CData. This is the statement, with which I try to add new data to the dataset:

datafile+=currwave;

However, this gives me the following error.

Quote:

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In function `int main(int, char**)':
error: invalid operands of types `CDataFile*' and `CData*' to binary `operator+'
error: in evaluation of `operator+=(class CDataFile*, class CData*)'

---

I'm a novice C++ writer, and I cannot figure out why it fails like this. It works, if I call the function as

datafile.operator+=(currwave);

and I am baffled why the actual operator overloading is causing havoc. Help!

I don't know why you get the errors to be honest.
Though, what is the type of datafile? It should be CDataFile* to match the return type of the overloaded operator. But then again I think it is CDataFile because you can call datafile.operator+=(currwave).

If datafile is the object and not a pointer to the object this should work:

Code:

---

CDataFile& CDataFile::operator+=(CData *wave) {
        CNode *node;
        node=new CNode((void *)wave);
        WaveList.AddTail(node);
        return *this;
}
...
CData *wave = new CData;
CDataFile datafile;
datafile += wave;

---

You say that both are instances of objects so I guess you have the returning type wrong. Though wave has to be a pointer not an instance

The datafile.operator+=(currwave) works because you ignore the returning type. Which should make you think: do you really want an overloaded operator? You should make and Add function and do datafile.Add(currwave). But of course you know best what you want

The operator += should take (const) and return a reference. So it becomes:

Code:

---

CDataFile& CDataFile::operator+=(const CData& wave)
{
        CNode* node;
        node=new CNode(wave);
        WaveList.AddTail(node);
        return *this;
}

---

Also, you should need to cast to void*, since it is implicit.
But no function should really take void* in C++, unless it is for C interoperability or compatibility. Instead, you should consider templates.