Custom Table Model
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dataChange takes a range so here you always emit that the it starts from the first up to the row you pass as parameter. Is it really always the case ?
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@EaccB said in Custom Table Model:
When emitting dataChanged(i,p) for the deleted row only,
You did not read my link. You must not call dataChanged() when removing a row.
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@EaccB said in Custom Table Model:
When emitting dataChanged(i,p) for the deleted row only,
You did not read my link. You must not call dataChanged() when removing a row.
Then what do I use to signal to the view that the model has been updated? I've removed dataChanged() and replaced it with layoutChanged() which seems to work fine.
To avoid any confusion, the table itself is read-only and should only reflect the contents of the students vector inside StudentManager. Any changes to the data (i.e. add student, edit student, remove student) are done directly on the students vector.
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@EaccB said in Custom Table Model:
Then what do I use to signal to the view that the model has been updated?
dataChanged() as explained above.
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@EaccB said in Custom Table Model:
Then what do I use to signal to the view that the model has been updated?
dataChanged() as explained above.
Ok, I'm really confused. You said that I shouldn't use dataChanged() when removing a row. So, what should I do when an element is removed from the vector? Or are you saying that I should emit dataChanged from the class which owns the vector and connect it to a slot in the Model?
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@EaccB said in Custom Table Model:
So, what should I do when an element is removed from the vector?
You really really should read the documentation. I already gave a the link two times...: https://doc.qt.io/qt-5/model-view-programming.html#inserting-and-removing-rows
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Ok, I'm really confused. You said that I shouldn't use dataChanged() when removing a row. So, what should I do when an element is removed from the vector? Or are you saying that I should emit dataChanged from the class which owns the vector and connect it to a slot in the Model?
@EaccB
To reiterate what @Christian-Ehrlicher is telling you. The signal code in a model has to depend on whether you are updating an existing row which is already there and will remain there, versus if you inserting or deleting a row.dataChanged()is only for same rows, with values in columns changing.For inserting/deleting rows you must use
begin/endInsert/RemoveRows()instead.Views, for example, need to know this and react differently according as the model reports its rows are being updated or are being deleted/inserted. You can imagine the action they take will differ between these cases.
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@EaccB
To reiterate what @Christian-Ehrlicher is telling you. The signal code in a model has to depend on whether you are updating an existing row which is already there and will remain there, versus if you inserting or deleting a row.dataChanged()is only for same rows, with values in columns changing.For inserting/deleting rows you must use
begin/endInsert/RemoveRows()instead.Views, for example, need to know this and react differently according as the model reports its rows are being updated or are being deleted/inserted. You can imagine the action they take will differ between these cases.
I think we got out wires crossed. By "update the vector", I meant add and remove elements, as well as editing existing items. This is why I was confused when @Christian-Ehrlicher suggested using dataChanged(), which he had previously told me not to use for removing elements.
If I add an element directly to the vector, do I still need to call insertRows() from the model?
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@EaccB said in Custom Table Model:
which he had previously told me not to use for removing elements.
where?
If I add an element directly to the vector, do I still need to call insertRows() from the model?
Yes, as clearly written in the docs.
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@EaccB said in Custom Table Model:
which he had previously told me not to use for removing elements.
where?
If I add an element directly to the vector, do I still need to call insertRows() from the model?
Yes, as clearly written in the docs.
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You must not call dataChanged() when removing a row.
@EaccB Sorry, I over read the not
This statement is correct.
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I think we got out wires crossed. By "update the vector", I meant add and remove elements, as well as editing existing items. This is why I was confused when @Christian-Ehrlicher suggested using dataChanged(), which he had previously told me not to use for removing elements.
If I add an element directly to the vector, do I still need to call insertRows() from the model?
If you use the model-as-interface-on-existing-data
@EaccB said in Custom Table Model:
editing existing items
- The item that owns the data should emit a signal after the item is modified, the model will connect to this signal and emit
dataChanged
I meant add and remove elements
- The item that owns the data should emit a signal before the item is added/removed, the model will connect to this signal and call
beginInsertRows/beginRemoveRows - The item that owns the data should emit a signal after the item is added/removed, the model will connect to this signal and call
endInsertRows/endRemoveRows
- The item that owns the data should emit a signal after the item is modified, the model will connect to this signal and emit
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