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How to Pass Non-Primitive Types Between C Signals and QML Slots?

Patricia Arquette
Patricia ArquetteOriginal
2024-11-02 16:26:29396browse

How to Pass Non-Primitive Types Between C   Signals and QML Slots?

Troubleshooting Signal-Slot Connection Between C and QML

In Qt, connecting signals from C classes to QML slots can sometimes encounter errors when dealing with non-primitive types. For instance, attempting to pass a QString from a C signal to a QML slot may result in the error: "Object::connect: No such slot QDeclarativeRectangle_QML_2::updateViewWithItem(QString)".

Solution: Using Connections

To resolve this issue, utilize QML connections instead of the traditional QObject::connect method. Here's how to implement it:

  1. Add the object to QML: In your C code, expose the myObj object to QML using setContextProperty.

    <code class="cpp">qmlVectorForm->rootContext()->setContextProperty("YourObject", myOb);</code>
  2. Define the signal: In your C class, declare the signal as follows:

    <code class="cpp">finishedGatheringDataForItem(QString signalString)</code>
  3. Add Connections in QML: In your QML file, define the connections like this:

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

By following these steps, you can establish a connection between the C signal and the QML slot, allowing you to pass and handle custom data types seamlessly.

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