Question

I have native C++ class SrcClass containing the following:

std::vector<shotEntry> objectsQueue;

bool getRelatedEntry(const entryToProcess *entriesDeets, int &i) const {
    if (i >= (int)objectsQueue.size()) {
        i = 0;
        return false;}
    if (!objectsQueue.size()) return false;
    entriesDeets = &(objectsQueue[i++]);
    return true;
}

In my client I have:

const entryToProcess *entriesDeets = NULL;
int i = 0;
while (srcObj->getRelatedEntry(entriesDeets, i)) {

When I step through getRelatedEntry the formal parameter, entriesDeets is updated as expected before returning. When it returns the actual parameter of the client is not updated.

This is in some big project I have returned to after two months away. I’m pretty sure the last refactoring I did was to introduce these damnable vectors. It takes ages to compile when I mess with headers. Am I getting confused with the initialize once/ readonly/ const’ness of C#? Can I get away with the client getting a read only native object back?

Answer 1

This is because you are setting the value of the function’s parameter. You want:

bool getRelatedEntry(const entryToProcess **entriesDeets, int &i) const {
    ...
    *entriesDeets = &(objectsQueue[i++]);
    ...

and

srcObj->getRelatedEntry(&entriesDeets, i)