Multiples Connections in QML

Antonio Ortiz

Hi, I'm trying to receive two jsonArrays from two different endpoints to build a list in QML with a Listview.
The json contains the same data structure, so I save the data in a single C++ object. In order to do that, I request the json from the first endpoint and then wait for the signal replyStatusChanged() to call a javascript controller that saves the json's content in the C++ object, and then repeat the process for the second one.
When I do this I encountered that the jsons arrives in any order an I need to wait for the first data to be fully loaded in the object before the writing of the second set of data starts.

How can I check if the data of the second endpoint has been received and the data of the first endpoint has been written?. I was thinking on using two signals but I don't know how to do it.

The classes

Class a : public QObject
{
     ...
     Q_INVOKABLE void get ();
     Q_INVOKABLE QJsonArray getJsonArray();
      signals:
     void replyStatusChanged();
}

 Class b : public QObject
 {
      //Contains the data
 }

the main fucntion

 int main(int argc, char *argv[])
 {
      a endpoint1;
      a endpoint2;
      b container;

      engine.rootContext()->setContextProperty("endpoint1", &endpoint1);
      engine.rootContext()->setContextProperty("endpoint2", &endpoint2);
      engine.rootContext()->setContextProperty("container", &container);
      ...

      return 0;
}

In the QML file

Connections
{
        target: endpoint1
        onReplyStatusChanged: controller.setData1()
}

Connections
{
    target: endpoint2
    onReplyStatusChanged: controller.setData2()
}

benlau

Not quite understand your question.. Generally speaking, Javascript application use a Promise object for deferred and asynchronous operation. For example , do something when two or more asynchronous operations completed (in any order).

Qt do not bundle any Promise implementation by default. You could get a one from my github repo:

benlau/quickpromise

Example


Promise {
  resolveWhen: Q.all([endpoint1. onReplyStatusChanged,endpoint2. onReplyStatusChanged]);
  onFulfilled: { // It will be triggered only if both of the endpoint emitted the signal
    controller.setData1();
    controller.setData2();
 }
}