Cycling through the items of TreeModel

Patou355

I need to cycle through the items of a TreeModel.
Example:

And I need to browse through them a bit like this:
anItem ; anotherItem ; aChild ; anotherChild ; andSoOn
Is there an iterator going through all the items or do I have to write a kind of "++" operator doing the tests (child is valid and so on)?

I'm writing something like that:

void itemIndexPlusPlus(QModelIndex &index){
    int indexRowBuf;
    if (index.child(0,0).isValid())//if has child
        index = index.child(0,0);
    else if (index.parent().child(index.row()+1, 0).isValid())//if has buddy following
        index = index.parent().child(index.row()+1, 0);
    else {
        while ((index != rootIndex())) {//ascend to the master excepted if children of row+1
            indexRowBuf = index.row();
            index = index.parent();
            if (index.child(indexRowBuf + 1, 0).isValid()) {
                index = index.child(indexRowBuf + 1, 0);
                break;
            }
        }
    }
}

But first it's not very stylish : long code and plenty of tests for something simple and then, I don't like to reinvent the wheel. Qt has plenty of wheels, but I sometimes have difficulties to find the good one...

Patrick.

VRonin

How about recursion? for example:

void printModel(const QAbstractItemModel* const model, const QModelIndex& parent = QModelIndex()) {
  const int rowCount = model->rowCount(parent);
  if(model->columnCount(parent) == 0) { return; }
  for(int i = 0; i < rowCount; ++i) {
    const QModelIndex currIdx = model->index(i, 0, parent);
    qDebug() << currIdx.data();
    if(model->hasChildren(currIdx)) {
      printModel(model, currIdx);      
    }
  }
} // printModel

then call it with printModel(treeModel);

Patou355

It seems to work.

Recursion was an old souvenir in my studies...

Thanks to you, you contributed to my programmer experience :)

Patou355

One question : why are all the arguments const ?

VRonin

It's the most permissive way. with all those consts you can call the function with arguments of any constness. for example:

QAbstractItemModel* model; printModel(treeModel); //works
const QAbstractItemModel* model; printModel(treeModel); //works
QAbstractItemModel* const model; printModel(treeModel); //works
const QAbstractItemModel* const model; printModel(treeModel); //works

Of course I could do that because all I do in that function is print values from model to the console. if you want to change values in the model you have to lose the first const so: void printModel(QAbstractItemModel* const model, const QModelIndex& parent = QModelIndex()) but now if you try to call it with a const model (const QAbstractItemModel* model; printModel(treeModel);) it will fail to compile