How to remove items from c++ model inside qml?

flashmozzg

My model is subclass of QAbstractListModel
What methods should I implement? I guess it's deleteRows but how do I "call" them inside of qml code? Especially if I don't have access to my model (or it's methods because of some strange qt magic which turns my model to QQmlDMAbstractItemModelData which has all the rolls but no methods, and I don't want to store my model as property in all qml delegates)
I mean then I do something like role = data it implicitly calls setData, when I just use role it uses data(). But how to make it remove current item (at index)?

p3c0

Hi @flashmozzg
You can create a Q_INVOKABLE function in C++ model which will internally call removeRow. Current item row can be retrieved from the QML itself and then pass to this function.

flashmozzg

@p3c0 said:

Hi @flashmozzg
You can create a Q_INVOKABLE function in C++ model which will internally call removeRow. Current item row can be retrieved from the QML itself and then pass to this function.

Yeah I ended up doing like that. With propagating remove signal to the top and then deleting it. Was hoping there was some built-in mechanism for doing that like there is for reading and modifying items data.

CoderJeff

I have the same question. But I did not solve it using removeRow.

In C++ (Q_INVOKABLE):
void MyCppClass::remove(const int idx)
{
bool bExe = mySqlModel->removeRow(idx);
}

In QML:
TableView {
id: tableView
......
}

Button{
onClicked: myCppClass.remove(tableView.currentRow);
}

The application output is:
QSqlQuery::value: unknown field name ''

Is there anything wrong with my code?

p3c0

@CoderJeff IsmySqlModel a subclass of QSqlQueryModel ?

CoderJeff

@p3c0
No, mySqlModel is a subclass of QSqlTableModel.

p3c0

@CoderJeff Are you sure tableView.currentRow returns a valid row ?

CoderJeff

@p3c0 said:

@CoderJeff Are you sure tableView.currentRow returns a valid row ?

Yes, I debug my code, and the input parameter idx is correct.

There are six rows. I checked each row's index: 0,1,2,3,4,5.

p3c0

@CoderJeff Ok. Not sure then. I guess there's some other code that is causing the problem.

CoderJeff

@p3c0

The entire code is the following.

In C++ (Q_INVOKABLE):
void MyCppClass::remove(const int idx)
{
bool bExe = mySqlModel->removeRow(idx);
}

(Q_INVOKABLE)
QObject* MyCppClass::selectModel()
{
return mySqlModel->selectModel();
}

MySqlModel* MySqlModel::selectModel()
{
QString strQuery("SELECT field1,field2,field3 FROM table WHERE field1='a'");
setQuery(QSqlQuery(strQuery));
return this;
}

TableView {
id: tableView
TableViewColumn{ role: "field1"; title: "Field1"}
TableViewColumn{ role: "field2"; title: "Field2"}
TableViewColumn{ role: "field3"; title: "Field3"}
model: myCppClass.selectModel()
......
}

Button{
onClicked: myCppClass.remove(tableView.currentRow);
}

p3c0

@CoderJeff Can you check if mySqlModel has data ?
You can check it by using record.

mySqlModel->record(idx).value(0).toString() // checking value at column 0 and converting it to string

CoderJeff

@p3c0

You are right. It is empty.

I will check the logic.

CoderJeff

@p3c0

A weird phenomenon. If using QSqlTableModel, the result is invalid. But if using QSqlQueryModel, the result is the expected.

Why?

The following is my debugging code.

MySqlModel* MySqlModel::selectModel()
{
QString strQuery("SELECT field1,field2,field3 FROM table WHERE field1='a'");

    QVariant val0;
    QVariant val1;

    setQuery(QSqlQuery(strQuery));
    val0 =  record(0).value(0);  //Invalid
    val1 =  record(0).value(1);  //Invalid

    QSqlQueryModel model;
    model.setQuery(strQuery);
    val0 =  model.record(0).value(0);  //Correct. The result is the expected.
    val1 =  model.record(0).value(1);  //Correct. The result is the expected.

return this;
}

p3c0

@CoderJeff According to the doc here, setTable should be used instead of setQuery for QSqlTableModel.

CoderJeff

@p3c0 said:

@CoderJeff According to the doc here, setTable should be used instead of setQuery for QSqlTableModel.

The cause is not as simple as I expected. Although I change MySqlModel's parent class to QSqlQueryModel instead of QSqlTableModel, it still does not work. But if using QSqlQueryModel directly, it works.

I am confusing.

class MySqlModel : public QSqlQueryModel
{
}

MySqlModel* MySqlModel::selectModel()
{
QString strQuery("SELECT field1,field2,field3 FROM table WHERE field1='a'");

QVariant val0;
QVariant val1;

//using MySqlQueryModel
setQuery(strQuery);
val0 =  record(0).value(0);  //Invalid
val1 =  record(0).value(1);  //Invalid

//using QSqlQueryModel directly
QSqlQueryModel model;
model.setQuery(strQuery);
val0 =  model.record(0).value(0);  //Correct. The result is the expected.
val1 =  model.record(0).value(1);  //Correct. The result is the expected.

return this;
}

p3c0

@CoderJeff Make sure the query is active before using setQuery.

QSqlQuery sq;
sq.prepare(strQuery);
sq.exec();
qDebug() << sq.isActive();
setQuery(sq);

CoderJeff

@p3c0 said:

@CoderJeff Make sure the query is active before using setQuery.
QSqlQuery sq;
sq.prepare(strQuery);
sq.exec();
qDebug() << sq.isActive();
setQuery(sq);

I tested it in your way, but It still did not work. The query is definitely active because the return value of isActive() is true.

p3c0

@CoderJeff Ok. Can you post your complete minimal runnable code somewhere in a zip to test ? Need to check whats actually going on.

CoderJeff

@p3c0 said:

@CoderJeff Ok. Can you post your complete minimal runnable code somewhere in a zip to test ? Need to check whats actually going on.

I sent you the link. Please check it.

p3c0

Hi @CoderJeff,
Your code looks fine. Use method1 or method3 in MySqlModel. The problem is with the view. TableView inside ScrollView seems to break. I just kept TableView in tab01 and everything worked as expected.