QAbstractListModel: How to use insertRows/removeRows if data is managed outside

[maxwell31]

Hi,

I want to make a QAbstractListModel which is a member of a class. Inside the model I would like to store a pointer to the actual data:

	std::vector<double> * _pos;

I understand how to implement rowCount and data but I wonder what I should do withinsertRows and removeRows if the contents of _pos are managed outside the model.

The implementation of my data function looks like this:

	case Position:
		return  QVariant::fromValue(_pos->at(index.row()));

[SGaist]

Hi,

How exactly is that data managed ?
Where does it come from ?

[JKSH]

@maxwell31 said in QAbstractListModel: How to use insertRows/removeRows if data is managed outside:

Inside the model I would like to store a pointer to the actual data:

How does your model know when the data has changed externally?

@maxwell31 said in QAbstractListModel: How to use insertRows/removeRows if data is managed outside:

I wonder what I should do withinsertRows and removeRows if the contents of _pos are managed outside the model.

It should either

• Modify the data and return true, OR
• Do nothing and return false

[maxwell31]

Well, maybe it would be bad design anyway, but this is how I thought it could be:

I have a c++ class, which has e.g. a std::vector<double> which I want to expose to qml via a QAbstractListModel. In this backend class, items can be added, modified, and deleted. I thought that instead of mirroring the vector inside my QAbstractListModel I could simply use the pointer to this vector in the QAbstractListModel, and call the necessary signals of QAbstractListModel in the backend class

[SGaist]

That's correct. Now the question are:

1. Where is that backend class modified in your code ?
2. What will modify the content of that vector ?