[PyQt] Public QAbstractItemModel methods (wrongfully?) made private in QAbstract(Table|List)Model?

[Elvis Stansvik]

2016-06-02 12:31 GMT+02:00 Phil Thompson <phil at riverbankcomputing.com>:
> On 2 Jun 2016, at 10:53 am, Florian Bruhin <me at the-compiler.org> wrote:
>>
>> * Elvis Stansvik <elvstone at gmail.com> [2016-06-02 10:36:32 +0200]:
>>> Hi all,
>>>
>>> From qabstractitemmodel.sip:
>>>
>>> In the declaration of QAbstractTableModel:
>>>
>>> private:
>>>    ...
>>>    virtual QModelIndex parent(const QModelIndex &child) const;
>>>    virtual bool hasChildren(const QModelIndex &parent) const;
>>>
>>> and in the declaration of QAbstractListModel:
>>>
>>> private:
>>>    ...
>>>    virtual QModelIndex parent(const QModelIndex &child) const;
>>>    virtual int columnCount(const QModelIndex &parent) const;
>>>    virtual bool hasChildren(const QModelIndex &parent) const;
>>>
>>> But these are all public functions in C++, and part of the public
>>> abstract item model API.
>>
>> No, they are private in C++ as well:
>> https://github.com/qtproject/qtbase/blob/dev/src/corelib/itemmodels/qabstractitemmodel.h#L381-L384
>> https://github.com/qtproject/qtbase/blob/dev/src/corelib/itemmodels/qabstractitemmodel.h#L407-L411
>>
>> I guess the rationale is that it makes no sense to ask e.g. how many
>> columns a list has?
>
> This is an interesting read...
>
> http://www.gotw.ca/publications/mill18.htm
>
>>> This leads to things like:
>>>
>>> [estan at pyret ~]$ cat test.py
>>> from PyQt5.QtCore import QStringListModel
>>> model = QStringListModel()
>>> model.hasChildren()
>>> [estan at pyret ~]$ python test.py
>>> Traceback (most recent call last):
>>>  File "test.py", line 3, in <module>
>>>    model.hasChildren()
>>> TypeError: QAbstractListModel.hasChildren() is a private method
>>>
>>> while the same works fine in C++.
>>
>> It does not for me:
>>
>> test.cpp: In function 'int main(int, char**)':
>> test.cpp:17:25: error: 'virtual bool QAbstractListModel::hasChildren(const QModelIndex&) const' is private within this context
>>     qsl->hasChildren(idx);
>
> However the C++ base class should be able to invoke a Python re-implementation. The "private" means that a sub-class cannot call the super-class implementation. This is a problem because there is then no way to fallback to the C++ implementation if there is no Python re-implementation.
>
> So - I don't think it can be made to work, so I'm inclined not to change anything...

Yes, fair enough. My original mail was based on a misunderstanding.

Elvis

>
> Phil
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