How to Pass a QString From a C Signal to a QML Slot?

Qt: Connecting C Signal to QML Slot with QString

In Qt, sending signals from C to slots in QML can be straightforward. However, when it comes to passing QString as a parameter, some challenges may arise.

The Issue:
You're connecting a signal from a C object (myObj) to a slot in a QML file (updateViewWithItem). The slot is defined to receive a QString parameter, but the connection fails with an error: "No such slot QDeclarativeRectangle_QML_2::updateViewWithItem(QString)".

The Solution: Using Connections

Instead of using conventional C -style slot-signal connections, Qt suggests employing Connections for this specific scenario.

Steps:

1. Expose Your C Object in QML:
   Set a context property in your QML file to make your C object (myObj) accessible to QML.

   <code class="cpp">qmlVectorForm->rootContext()->setContextProperty("YourObject", myOb);</code>

2. Define Your Signal:
   Your signal should be defined as follows:

   <code class="cpp">finishedGatheringDataForItem(QString signalString)</code>

3. Create the QML Connection:
   Within your QML file, add a Connections object to handle the connection.

   <code class="qml">Connections {
       target: YourObject
       onFinishedGatheringDataForItem: {
           qmlString = signalString
       }
   }</code>

By using Connections, you effectively establish a new bridge between C and QML, allowing you to pass QString as a parameter to the QML slot.

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