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

CoderJeff

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.

CoderJeff

@p3c0 said:

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.

What's the meaning of "kept TableView in tab01"? Can you show me the code?

p3c0

@CoderJeff The contents of tab01.qml file. I just TableView in it and deleted the rest. It works.

//Tab01.qml

import QtQuick 2.0
import QtQuick.Controls 1.2
import QtQuick.Layouts 1.1

TableView{
    id: tableView
    anchors.fill: parent
    TableViewColumn{ role: "id"; title: "Id"}
    TableViewColumn{ role: "name"; title: "Name"}
    TableViewColumn{ role: "author"; title: "Author"}
    TableViewColumn{ role: "year"; title: "Year"}
    model:myCppClass.model()
}

CoderJeff

@p3c0

I got it.

Yes, it works. I change ScrollView to Rectangle, and it also seems work well. But I debugged the code, and fount that the value of val0 and val1 in method1 and method3 were still not right.

Did you check them?

p3c0

@CoderJeff Hmm that's strange. It doesn't work. Tested it with my other project, works there.

p3c0

@CoderJeff If you replace the code in data() with the following, it will work:

QVariant MySqlModel::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return QVariant();

    switch(role) {
        case Id: {
            return record(index.row()).value(0).toString();
        }
        case Name : {
            return record(index.row()).value(1).toString();
        }
        case Author : {
            return record(index.row()).value(2).toString();
        }
        case Year : {
            return record(index.row()).value(3).toString();
        }
    }
    return QSqlQueryModel::data(index, role);
}

...

setQuery(strQuery);
var0 = record(1).value(0);
var1 = record(0).value(1);
qDebug() << var0 << var1;

Trying to find the reason.

CoderJeff

@p3c0

That's what I am confused with. In addition, I tested the following statements, and they all works.

record(0).indexof(...)
record(0).index(...)
data(...)

I do not understand why only record(0).value(...) can not work.

I tried to delete a chosen row, but it could not.I do not know whether it is the above reason. I have updated my code. Can you please check them? Thank you.

CoderJeff

@p3c0 said:

@CoderJeff If you replace the code in data() with the following, it will work:

QVariant MySqlModel::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return QVariant();

    switch(role) {
        case Id: {
            return record(index.row()).value(0).toString();
        }
        case Name : {
            return record(index.row()).value(1).toString();
        }
        case Author : {
            return record(index.row()).value(2).toString();
        }
        case Year : {
            return record(index.row()).value(3).toString();
        }
    }
    return QSqlQueryModel::data(index, role);
}

...

setQuery(strQuery);
var0 = record(1).value(0);
var1 = record(0).value(1);
qDebug() << var0 << var1;

Trying to find the reason.

Yes, it works. The value of val0 and val1 are both right this time. But I still can not delete a row.

p3c0

@CoderJeff That is because QSqlquerymodel is a read-only model. See here. You will need to delete the row using another query and then update the view.

CoderJeff

@p3c0

I tried to use QSqlTableModel, and it also did not work.

Here I do not want to use another query. I just want to delete a row from the model instead of the table. In other words, only on GUI it seems to be deleted, but it is still in the table actually.

p3c0

@CoderJeff Sorry I too donot know about this. This QTBUG-37538 seems to be similar but using ListView.
Test it with QTableView to see if it works ?

CoderJeff

@p3c0

I used a temporary table to achieve my expected function. In addition, call setTable and select as the SqlTableModelTest did.

p3c0

@CoderJeff Ok, but then why not execute a delete query instead of creating another temporary table ? I guess removeRow for QSqlTableModel too does the same internally.