How to make a QSet hold structs?

[wayfaerer]

I'm a bit confused, because I thought QSet could hold structs, but I keep getting an error "c:\QtSDK\Desktop\Qt\4.7.4\mingw\include\QtCore\qh ash.h:880: error: no matching function for call to 'qHash(const NoteStruct&)'"

Here's the struct:

struct NoteStruct
{
    float startPosition;
    float width;
    QGraphicsItem *noteLane;
    int velocity;
};

struct NoteStruct
{
    float startPosition;
    float width;
    QGraphicsItem *noteLane;
    int velocity;
};

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Here's the offending method:

void SequencerScene::copy()
{
    currentlyCopiedNotes.clear();
 
    foreach (QGraphicsItem *note, selectedItems())
    {
        NoteStruct newNote;
        newNote.startPosition = note->transform().dx();
        newNote.width = note->boundingRect().width();
        newNote.noteLane = note->parentItem();
        newNote.velocity = static_cast<Note*>(note)->getVelocity();
 
        currentlyCopiedNotes.insert(newNote); // THIS IS THE OFFENDING CODE
    }
}

void SequencerScene::copy()
{
    currentlyCopiedNotes.clear();

    foreach (QGraphicsItem *note, selectedItems())
    {
        NoteStruct newNote;
        newNote.startPosition = note->transform().dx();
        newNote.width = note->boundingRect().width();
        newNote.noteLane = note->parentItem();
        newNote.velocity = static_cast<Note*>(note)->getVelocity();

        currentlyCopiedNotes.insert(newNote); // THIS IS THE OFFENDING CODE
    }
}

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And here's the declaration of currentlyCopiedNotes (in the header file):

private:
    QSet<NoteStruct> currentlyCopiedNotes;

private:
    QSet<NoteStruct> currentlyCopiedNotes;

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The reason I'm trying to do this is that I am creating a way to copy notes (QGraphicsItems) in a QGraphicsScene, so that they can be pasted afterwards. The NoteStruct is a struct containing the attributes of the notes.

I'd appreciate some advice... thanks!

[Zlatomir]

Your type needs to have a operator==() and also a global qHash(const NoteStruct&)
You can see the reference page here

[ChrisW67]

...and be wary of the floats if they are part of your equality test.