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pyqtqtreeviewqabstractitemmodel
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Reputation: 19379

PyQt: QTreeView and QAbstractItemModel in human language

While diving deep into TreeView/Model concept here is what I "understand" so far...

First I subclass MyTreeView() class where I extend a QTreeView build-in by assigning it to MyOwnAbstractItemModel() model (subclassing in a next step):

class myTreeView(QTreeView):
    def __init__(self, parent=None):
        super(myTreeView, self).__init__(parent)
        self.myOwnAbstractModel = MyOwnAbstractItemModel()
        self.setModel(self.myOwnAbstractModel)

I continue with subclassing/describing MyOwnAbstractItemModel(). It uses a built-in QAbstractItemModel() class as a "template" to start with...

class MyOwnAbstractItemModel(QAbstractItemModel):      
    def __init__(self, parent=None):
        super(MyOwnAbstractItemModel, self).__init__(parent)

From what I understand there are some MyOwnAbstractItemModel() methods that must be declared for MODEL to work. I wonder where could I get a complete list of those method() names and their syntax description?

I looked at the code examples posted online. It appears those pre-defined methods have a specific syntax already pre-defined... such as number of incoming arguments and what type of arguments is expected... for example the method below dosen't get any incoming arguments (not clear what a purpose of it):

def mimeTypes(self):
    #print '\n mimeTypes(self)'
    types = QStringList()
    types.append('application/x-ets-qt4-instance')
    return types

But this method:

def dropMimeData(self, mimedata, action, row, column, parentIndex):
    parentNode = self.nodeFromIndex(parentIndex)

takes four arguments. Please advice! Many thanks in advance.

Upvotes: 2

Views: 2665

Answers (2)

ekhumoro
ekhumoro

Reputation: 120798

If you download the source code for PyQt, you will find a model-testing module in the contrib/pymodeltest directory. This module provides a way to check for the common errors found in custom model implementations. You may find it useful to look through the code in this module, as it has a lot of helpful comments that explain the purpose of many of the tests it performs.

Also, you should read through the Model/View Programming overview in the Qt Docs - in particular the Model Subclassing reference.

Upvotes: 4

hackyday
hackyday

Reputation: 1329

The Qt documentation lists the minimum methods needed to subclass QAbstractItemModel in the docs.

The method signatures are set to accept certain arguments because that is how the classes that interact with the model (e.g. views), will call them. The couple of examples you gave have to do with implementing drag-and-drop functionality.

With the tree model, you may also want to implement certain methods in a node data class so that your tree nodes can provide information about themselves, their parent and children. How you do this is up to you. These nodes link together to form the tree hierarchy.

The model/view stuff can be a little difficult to wrap your head around at first. I might suggest implementing your own tree model and using the standard QTreeView at first, and then exploring custom views and drag-and-drop from there. The simpletreemodel example provided with the PyQt source is a good bare bones example. It implements only only the required method (plus headerData), and has a simple TreeItem class as nodes.

Upvotes: 2

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