removing item in qlistwidget through string

Pogi

is there a function in QListWidget class like QListWidget::remove("item");

or should i make a loop and find the item every index?

asif_cse

This something like :

QListWidget::removeItemWidget(QListWidgetItem * item)

Pogi

in http://www.qtcentre.org/threads/9343-remove-item-from-QListWidget
it says QListWidget::removeItemWidget(QListWidgetItem * item) doesnt delete the item.

so i did this :
for ( int a = 0; a < ui->clientList->count()+1; a++ )
{
if ( ui->clientList->item(a)->text() == QString::fromStdString(name) )
{
delete ui->clientList->takeItem(a);
}
}

any better solution?

jsulm

remove +1 in

for ( int a = 0; a < ui->clientList->count()+1; a++ )

If you want to remove everything you can just call

ui->clientList->clear();

Chris Kawa

@Pogi
takeItem changes the count and the item at current index so your loop skips an item every time you take something from it. It's generally bug-prone to modify any container you're looping through.
Also constructing the same string in every loop pass is not a good idea.

What you can do instead is this:

qDeleteAll(ui->clientList->findItems(QString::fromStdString(name), Qt::MatchFixedString));

Pogi

@Chris-Kawa
takeItem changes the count and the item at current index
im aware of that thanks, i dont have any problem here since i only need to delete one item. also i forgot to put break inside the if statement so you thought i will delete multiple items in one set of loop

Also constructing the same string in every loop pass is not a good idea.
what do you mean?

and ive noticed that this code:

        for ( int a = 0; a < ui->clientList->count(); a-- )
        {
            if ( ui->clientList->item(a)->text() == QString::fromStdString(name) )
            {
                delete ui->clientList->takeItem(a);
                break;
            }
        }

can only delete the first item, i mean let say i have 3 items in my QListWidget object.
if the if statement is true and a is 0, it deletes the item at row 0 successfully
but if the if statement is true and a is 1 or 2, it doesnt delete the item, it only highlights the item as if you mouseclick on it.

Chris Kawa

what do you mean?

I mean this: QString::fromStdString(name). It creates new instance of QString, allocates storage and makes a copy of the std::string data. And you're doing it in every loop pass while you could be doing it once in advance.

for ( int a = 0; a < ui->clientList->count(); a-- )

You're starting at 0 and then you a-- into oblivion ;)

You could of course start at the end and iterate backwards, but isn't a straight one-liner better than an 8 line loop with conditional expression? It's easier to read and very hard to get wrong (no loops, ifs, counters and breaks...).

Pogi

@Chris-Kawa
It creates new instance of QString, allocates storage and makes a copy of the std::string data
i dont know that, i thought its just like a static casting or stream

You're starting at 0 and then you a-- into oblivion
that was just a typo, it is actually a++ in my code

this one does nothing:
qDeleteAll(ui->clientList->findItems(QString::fromStdString(name), Qt::MatchFixedString));
can you link me the documentation for qDeleteAll?

EDIT: nevermind the documentation i found it

Pogi

qDeleteAll(ui->clientList->findItems(QString::fromStdString(name), Qt::MatchFixedString));

this does the same as my for loop, it highlights the item as if you mouseclicked on it
is it a bug?

Chris Kawa

dont know that, i thought its just like a static casting or stream

It's not. It's a copy and conversion to UTF.

this one does nothing

It does what you wanted - removes and deletes all QListWidgetItems with given text. If it doesn't then there must be something else wrong in your code. Can you make a minimal example that shows the problem?

Pogi

@Chris-Kawa

Can you make a minimal example that shows the problem?
it can only delete the first item in the QListWidget object.

im making a chat app. when a user disconnects, he will be disconnected and his/her name will be removed in the QListWidget.

im using SFML network

so this my destructor for client, it runs when that client disconnects.
ClientManager::~ClientManager()
{
sf::Packet name;
name << Login::getName().toStdString();
if ( client.send(name) == 0 )
{
//successfully sends the name of the client the disconnects
// the server will receive its name and send the info to all clients
}
}

void ClientManager::receiveMessage()
{
if ( client.receive(packet) == 0 )
{
emit displayMessage();
}
}

slot:
void MainWindow::displayMessage()
{
qDebug() << QString::fromStdString(name) << " has been disconnected";
qDeleteAll(ui->clientList->findItems(QString::fromStdString(name), Qt::MatchFixedString));

}

minimal example for server side:
void ServerManager::ReceivePacketAndSendToAllClientExceptTheSender()
{

}

as you can see in the displayMessage() slot function, the:
qDebug() << QString::fromStdString(name) << " has been disconnected";
prints correctly, so the name received from the server is correct, so i think the only wrong is qDeleteAll(); im lost now :(

Pogi

@Chris-Kawa I have fixed it, you're right. it is something else in my code.
i just found and realized it when another part of my program is showing the problem, this time the problem is showing more detailed so i managed to find out.