Best way to pass data from backend c++

Hi, I need to link the data from the classes connected to the backend, for example I have this class where it receives the data from the server through this method:

Code:

---

void ClientServices::readyRead()
{
   QDataStream in(tcpSocket);//QtcpSocket
 
    int code = 0;
    double pCost = 0;
    double pPublic = 0;
 
    in >> code >> pCost >> pPublic;
 
    qDebug() << code << pCost << pPublic;
 
 
}

---

the Backend is declare in this mode:

qmlRegisterType<Backend>("io.qt.Backend", 1, 0, "Backend");

can I do?

I think to do with the Q_Property but but I wouldn't go for the backend anymore. In practice I have to fill in text boxes with variable :

code >> pCost >> pPublic;

see my schema:
Attachment 13047

Since your other thread suggests that you will get multiple "rows" of these three values, the best way to present these rows of values to QML/QtQuick is a list model.

The ClientService object needs to notify the model about new incoming data, maybe via signal.

Easiest way is probably to do all the object creation and connecting on the C++ side and simply expose the fully working model to QML via QQmlContext::setContextProperty() on the engine's rootContext().

Cheers,
_

I think I'll follow your path,when I have done I'll show you,tanks for help me

there are almost, the signal emit sendCode (c_code); is data download, I will look in the qml when I call it "ReferenceError: c_code is not defined" error
Attachment 13050

this is my code Qml:

Code:

---

Backend {
        id: backend
 
        onSendCode: {
            console.log( "This is code---> " + c_code);
        }
 
    }

---

Good moorning it give me a error in the row 16: ReferenceError: code is not defined

this is my Riparazioni.qml

Code:

---

import QtQuick 2.10
import QtQuick.Controls 2.3
import io.qt.Backend 1.0
 
Item
{
id: element
 
Backend {
    id: backend
 
    onSendCode: {
 
        console.log( "This is code---> " + code); // errrrrrrrrrorrrrrrrr
    }
 
}
 
 
Row {
    id: row1
    height: 50
    anchors.right: parent.right
    anchors.rightMargin: 5
    anchors.left: parent.left
    anchors.leftMargin: 5
    anchors.top: parent.top
    anchors.topMargin: 3
 
    Rectangle {
        id: rectangle_Search
        height: 44
        color: "#0e99b2"
        anchors.top: parent.verticalCenter
        anchors.topMargin: -25
        anchors.left: parent.left
 
        anchors.right: parent.right
 
 
        Text {
            id:lbl_SearchCode
            color: "#0a0808"
            text: qsTr("Codice")
            anchors.verticalCenter: parent.verticalCenter
            anchors.left: parent.left
            anchors.leftMargin: 4
            font.pixelSize: 12
        }
 
        CustomTextEdit {
            id: c_Txt_codice
            y: 0
            width: 50
            height: 20
            anchors.verticalCenter: parent.verticalCenter
            anchors.bottom: parent
            anchors.bottomMargin: 0
            anchors.left: lbl_SearchCode.right
            anchors.leftMargin: 20
 
        }
 
        CustomButton {
            id: btnSearchKey
            x: 583
            y: 3
            text: "S"
            anchors.verticalCenter: parent.verticalCenter
            anchors.right: parent.right
            anchors.rightMargin: 5
            anchors.top: parent.verticalCenter
            anchors.topMargin: -22
            color: enabled ? this.down ? "#78C37F" : "#87DB8D" : "gray"
            onClicked: {
                // backend.connectClicked()
                backend.connectClicked()
                backend.sendClicked(c_Txt_codice.text)
            }
        }
 
    }
}
Row {
    id: row2
    height: 200
    anchors.right: parent.right
    anchors.rightMargin: 3
    anchors.left: parent.left
    anchors.leftMargin: 3
    anchors.top: row1.bottom
    anchors.topMargin: 2
 
    Rectangle{
        id: rectangle_Articolo
        color: "#0e99b2"
        anchors.fill: parent
 
 
 
        Label{
            id: lbl_NBusta
            color: "#ebedef"
            text: "N°Busta"
            anchors.left: parent.left
            anchors.leftMargin: 5
            anchors.top: parent.top
            anchors.topMargin: 10
        }
 
        CustomTextEdit {
            id: txtCodice
            width: 40
            height: 18
            anchors.top: parent.top
            anchors.topMargin: 10
            anchors.left: lbl_NBusta.right
            anchors.leftMargin: 10
        }
 
    }
 
}
}

---

this is my main.cpp

Code:

---

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
 
    QGuiApplication app(argc, argv);
 
    //Pass my c++ to Qml
 
    //qmlRegisterType<ClientServices>("io.qt.Clienteservices", 1, 0, "Clientservices");
 
 
    qmlRegisterType<Backend>("io.qt.Backend", 1, 0, "Backend");
//    Backend backend;
 
//    QQmlContext *context = engine.rootContext();
//    context->setContextProperty("backend",&backend);
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
 
 
    if (engine.rootObjects().isEmpty())
        return -1;
 
    return app.exec();
}

---

this is the Signal with send at Riparazioni.qml and I have do the debug it has data:

Attachment 13051

How is the sendCode() parameter called in the signal's declaration?

And: have you decided against using a model?

Cheers,
_

in the backend constructor

Code:

---

#include "backend.h"
 
Backend::Backend(QObject *parent) : QObject(parent)
{
    client = new ClientServices("192.168.1.72",6547);
 
    connect(client, &ClientServices::hasReadSome, this, &Backend::receivedSomething);
    connect(client, &ClientServices::statusChanged, this, &Backend::setStatus);
    // FIXME change this connection to the new syntax
    connect(client->tcpSocket, SIGNAL(error(QAbstractSocket::SocketError)),
            this, SLOT(gotError(QAbstractSocket::SocketError)));
 
    //connect data to source database
    connect(client, &ClientServices::sendRiparazione, this ,&Backend::recivedRiparazione);
 
 
}
 
 
bool Backend::getStatus()
{
    return client->getStatus();
}
 
void Backend::setStatus(bool newStatus)
{
    //qDebug() << "new status is:" << newStatus;
    if (newStatus)
        { emit statusChanged("CONNECTED"); }
    else
    { emit statusChanged("DISCONNECTED"); }
}
 
void Backend::recivedRiparazione(int code, double p_pCosto, double p_Pubblico)
{
    emit sendCode(code);
    emit sendPCosto(p_pCosto);
    emit sendPPubblico(p_Pubblico);
 
}
 
void Backend::receivedSomething(QString msg)
{
    emit someMessage(msg);
}
 
 
 
void Backend::gotError(QAbstractSocket::SocketError err)
{
    //qDebug() << "got error";
    QString strError = "unknown";
    switch (err)
    {
        case 0:
            strError = "Connection was refused";
            break;
        case 1:
            strError = "Remote host closed the connection";
            break;
        case 2:
            strError = "Host address was not found";
            break;
        case 5:
            strError = "Connection timed out";
            break;
        default:
            strError = "Unknown error";
    }
 
    emit someError(strError);
}
 
void Backend::connectClicked()
{
    client->connect2host();
}
 
void Backend::sendClicked(QString msg)
{
    QByteArray arrBlock;
    QDataStream out(&arrBlock, QIODevice::WriteOnly);
    //out.setVersion(QDataStream::Qt_5_10);
    out << quint16(0) << msg;
 
    out.device()->seek(0);
    out << quint16(arrBlock.size() - sizeof(quint16));
 
    client->tcpSocket->write(arrBlock);
}
 
void Backend::disconnectClicked()
{
    client->closeConnection();
}

---

this is clientService.cpp:

Code:

---

#include "clientservices.h"
#include <QBuffer>
 
 
ClientServices::ClientServices(const QString hostAddress, int portNumber) : QObject (),m_nNextBlockSize(0)
{
    status = false;
    tcpSocket = new QTcpSocket();
 
    host = hostAddress;
    port = portNumber;
 
    timeoutTimer = new QTimer();
    timeoutTimer->setSingleShot(true);
    connect(timeoutTimer, &QTimer::timeout, this, &ClientServices::connectionTimeout);
 
    connect(tcpSocket, &QTcpSocket::disconnected, this, &ClientServices::closeConnection);
 
}
 
bool ClientServices::getStatus(){return status;
                                }
 
void ClientServices::closeConnection()
{
    timeoutTimer->stop();
 
    //qDebug() << tcpSocket->state();
    disconnect(tcpSocket, &QTcpSocket::connected, 0, 0);
    disconnect(tcpSocket, &QTcpSocket::readyRead, 0, 0);
 
    bool shouldEmit = false;
    switch (tcpSocket->state())
    {
        case 0:
            tcpSocket->disconnectFromHost();
            shouldEmit = true;
            break;
        case 2:
            tcpSocket->abort();
            shouldEmit = true;
            break;
        default:
            tcpSocket->abort();
    }
 
    if (shouldEmit)
    {
        status = false;
        emit statusChanged(status);
    }
 
}
 
void ClientServices::connect2host()
{
 
    timeoutTimer->start(3000);
 
    tcpSocket->connectToHost(host, port);
    connect(tcpSocket, &QTcpSocket::connected, this, &ClientServices::connected);
    connect(tcpSocket, &QTcpSocket::readyRead, this, &ClientServices::readyRead);
}
 
void ClientServices::readyRead()
{
   QDataStream in(tcpSocket);//QtcpSocket
 
    in >> code >> pCost >> pPublic;
 
    qDebug() << code << pCost << pPublic;
 
    emit sendRiparazione(code,pCost,pPublic);
 
}
 
void ClientServices::connected()
{
    status = true;
    emit statusChanged(status);
 
}
 
void ClientServices::connectionTimeout()
{
    //qDebug() << tcpSocket->state();
    if(tcpSocket->state() == QAbstractSocket::ConnectingState)
    {
        tcpSocket->abort();
        emit tcpSocket->error(QAbstractSocket::SocketTimeoutError);
    }
}

---

my Idea Controller Backend.cpp Model clientservice.cpp(and Other) View clsses Qml

Interesting but neither of the two code sections contains the declaration of the sendCode() signal.

The argument name in that declaration is the name available on the QML side.
It is irrelevant how the variable is called to you pass at emit time.

Cheers,
_

Backend.h

Code:

---

#ifndef BACKEND_H
#define BACKEND_H
 
#include <QObject>
#include "clientservices.h"
 
class Backend : public QObject
{
    Q_OBJECT
    Q_PROPERTY(bool currentStatus READ getStatus NOTIFY statusChanged)
public:
    explicit Backend(QObject *parent = nullptr);
     bool getStatus();
 
signals:
     void statusChanged(QString newStatus);
     void someError(QString err);
     void someMessage(QString msg);
     void sendCode(int c_Code);
     void sendPCosto(double p_pCosto);
     void sendPPubblico(double p_pPubblico);
 
public slots:
 
     void setStatus(bool newStatus);
 
     void recivedRiparazione(int code,double p_pCosto,double p_Pubblico);
     void receivedSomething(QString msg);
     void gotError(QAbstractSocket::SocketError err);
     void sendClicked(QString msg);
     void connectClicked();
     void disconnectClicked();
private:
     ClientServices *client;
     int codiceBusta;
     double prezzoCosto,prezzoPubblico;
 
};
 
#endif // BACKEND_H

---

---

Added after 19 minutes:

you say i should declare the variable code? I'm following this wiki

Quote:

---

Originally Posted by Nio74

Code:

---

void sendCode(int c_Code);

---

---

Code:

---

onSendCode: console.log("code=" + c_Code);

---

Cheers,
_

what a fool I am now works thanks