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

CoderJeff

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.

CoderJeff

@p3c0

Is a table not necessary when using a delete query?

p3c0

@CoderJeff table is required ofcourse but why duplicate it first. What you require can be achieved by firing another delete query and then reloading the model so that it reflects in TableView.

CoderJeff

@p3c0

Actually, I was wondering what you said for an evening, and still did not understand it. Can you show me an example?

If not duplicate the table first, after deleting a record from the table, how can I restore it?

p3c0

@CoderJeff Since you only want to delete a row it can be done as follows:

//MySqlModel.cpp
void MySqlModel::removeMyRow(int r)
{
    QString strQuery("DELETE FROM Book where id="+QString::number(r));
    QSqlQuery sq;
    sq.prepare(strQuery);
    sq.exec();

    strQuery = "SELECT * FROM Book";
    sq.prepare(strQuery);
    sq.exec();
    setQuery(sq);
}

This will delete the row first and then reload the model with updated data.

CoderJeff

@p3c0

That is not what I mean.

I just want to delete a row on GUI, not from the table. What you did will definitely delete a row from the table.

p3c0

@CoderJeff Oh. Sorry, I thought its other way. Didn't understood what you meant here.