Serializing a widget

JonB

@EL-jos
OK, sorry, I know nothing about whatsapp. I'd be very surprised if it "serialized widgets", but that's all I can say.

mrjj

Hi
For each message , date and time, you would save and index number telling
where in conversation it comes and some sort of ID for the message .
and most likely also a conversation id.

So you store the messages in one table
TABLE: messages
msgID, message text,
msgID, message text, etc
and make a table to list
conversation id, msgID
In other table
and most likely the persons also in other table with reference to conversations they
have taken part in.

But how are your data structured now ?

EL-jos

in fact for the data structure when I try to create a table and its values it does not work, here is my query:

    base = QSqlDatabase::addDatabase("QSQLITE");
    base.setDatabaseName("AMIS");
    if(base.open()){

        QSqlQuery query(base);
        qDebug() << query.exec("CREATE TABLE `test`.`amis` ( `id` INT NOT NULL AUTO_INCREMENT , `nom` VARCHAR(20) NOT NULL , `image` BLOB NOT NULL , PRIMARY KEY (`id`)) ");
    }

I always have false as the answer to the console output so my table is not created,

I even tried to remove the apostrophes on name, id and image but it still doesn't work.

Anybody got any ideas?

6thC

Well, first I'd say:
General advice is always use prepared statements.
Prepare: https://stackoverflow.com/questions/5609245/qsqlquery-prepared-statements-proper-usage

More general advice is figure out the actual query you sent the engine by firing a verbatim copy of the query generated in your application directly @ the engine without the application.

So, how I see it:

Determine the actual statement
run it at the engine (using with command line or query / db engine tools and see the response - independent from your application anyhow).
Witness the engine response as a result of your statement (I'm expecting a syntax error as it seems you are too)
This will lead you to the reasons what is not being correctly done in your application.
Fix the application statement
Try again

I suspect it would be a parsing error as you're playing with the single quotes but cannot say. I also won't troubleshoot what seems just syntax/parsing... that's for you to determine / observe.

EL-jos

Hey, family,

After a lot of testing, I understood that my database and my amis table are created but except that the amis table contains no columns so no fields.
I tried to add the plugin qsqlited.dll and qsqlmysqld.dll since I compiled in debug mode but my amis table is still empty so no amis.
Here's my code:

 QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName("base_de_donnees2.db");
    db.open();
    if(!db.isOpen())
        qDebug() << "ERREUR d'ouverture de la base de données; cause: " << db.lastError().text();
    QSqlQuery q;
    q.exec("CREATE TABLE IF NOT EXISTS amis (id INTEGER PRIMARY KEY AUTOINCREMENT, nom TEXT NOT NULL, photo BLOB NOT NULL) ");

    QSqlQuery q2;
    q2.prepare("INSERT INTO amis (id,nom,photo) VALUES (:id,:nom,:photo) ");

    int identifiant = 1;
    QString pseudo("EL-chrino");
    QFile fichier(QFileDialog::getOpenFileName());
    fichier.open(QIODevice::ReadOnly);
    QByteArray byte;
    if(!fichier.isOpen())
        qDebug() << "Echec d'ouverture du fichier";
    byte = fichier.readAll();

    q2.bindValue(":id",identifiant);
    q2.bindValue(":nom",pseudo);
    q2.bindValue(":photo",byte);

    if(!q2.exec())
        qDebug() << "ERREUR lors de l'exécution de la requête; cause: " << q2.lastError().text();

Note that I have never used databases with Qt so I don't know how it works, please tell me what I need to do to use databases with Qt as it will be very important for my chatt software.
Thank you in advance

EL-jos

I found in a forum, they say you need to recompile Qt and SQL Drive but it doesn't explain how to do it.

Please if there is someone who knows how to make it watch you manifest

mrjj

@EL-jos
Hi
For QSQLITE
you need to compile nothing or add any libraries.
just
QT += sql
in your .pro file

EL-jos

Thank you very much for your advice, but I have two questions;
first how to update a QscrollArea that already contains elements beforehand?
and the second is how to make a message waiting list like this if a client "A" has just logged out and another client "B" sends him a message, that the message is in a list to wait for the client "A" to read it.
like whatsapp or facebook notification when someone sends us a message while we're away, the message is kept until we read it?

SGaist

Hi,

You just append new widgets to the layout that already contains the others.

As for the messages, if you are thinking on how it’s working on mobile platform, you’ll have several things to take into consideration.

So some questions for you:

On what platform(s) is your application going to run ?
How are the client going to talk to each other ?

EL-jos

Regarding the update of my scroollArea, I don't want to add elements but rather delete completely what it already contains.

then for the messages I want my application to run all over the platform but first on Pc using the windows operating system.

for my clients, I use TCP/ip protocol so with QTcpSocket class

SGaist

The most elegant would likely be to have the messages stored in a model and then have a custom QStyledItemDelegate to paint whatever you want.

Again: how are you client talking to each other ? Through a central server ? How do they know each other ?

EL-jos

Hi,

Yes I use a server for the dialog between client, this means that if a client'A' sends a message to client'B', it will first go through the server then the server will send me to the destination so client'B'.

EL-jos

please someone has an idea.

mrjj

@EL-jos
About ?

EL-jos

In fact I want to make sure that if we send a message to a client that is not connected, that this client sees the message that has been sent as soon as it is connected.

JKSH

@EL-jos said in Serializing a widget:

I want to make sure that if we send a message to a client that is not connected, that this client sees the message that has been sent as soon as it is connected.

Then the central server must store the message. When the client comes online, the server can deliver the message to the client.

Note: This concept is about communications architecture. This is not related to widgets at all.

EL-jos

ahhhhh yes you're right, so I can store the message in a database at the server level then as soon as the concerned client is connected the server will be able to restore the message then send it to the client, thank you very much.

then a second unresolved problem so far;
here I have a scrollArea which first contains many widgets of different type, so I want to delete either empty all these widgets and left the scrollArea blank so without element,
how do I do that?

JKSH

@EL-jos said in Serializing a widget:

here I have a scrollArea which first contains many widgets of different type, so I want to delete either empty all these widgets and left the scrollArea blank so without element,
how do I do that?

Have a read through http://doc.qt.io/qt-5/qscrollarea.html . Do you see anything that might do what you want?

EL-jos

I just read and reread the Qt documentation for the QScrollArea class or even its mother classes but I can't find the solution to my problem because there is not a function that allows to remove all widgets contained in a scrollAreea

mrjj

@EL-jos
Hi
Are the widgets not in a layout ?
You can clear layout with

void clearLayout(QLayout *layout)
    QLayoutItem *item;
    while((item = layout->takeAt(0))) {
        if (item->layout()) {
            clearLayout(item->layout());
            delete item->layout();
        }
        if (item->widget()) {
            delete item->widget();
        }
        delete item;
    }
}