Uploaded image for project: 'Qt for MCUs'
  1. Qt for MCUs
  2. QTMCU-240

required property behaves differently from the big qt

    XMLWordPrintable

Details

    • 453db521, 71c8ffad, 2a0ad1d5

    Description

      there's something called required property in big qt(https://doc.qt.io/qt-6/qtqml-syntax-objectattributes.html#required-properties).

      one of the effects of the required property mentioned in the doc above is that the qml file instanciating a custom qml type with a required property must initialize that required property, otherwise an error occurs.

      however in qt for mcus, the behavior seems to differ.

      with the code below:

      // MyComponent.qml
import QtQuick
Text {
    required property int a
    Item {    }
}

// RequiredExperiment.qml <-- main qml file
import QtQuick
Rectangle {
    MyComponent {
        anchors.centerIn: parent
        text: "Qt for MCUs"
    }
}

      i got this error:

      C:/Users/81808/Downloads/RequiredExperiment/MyComponent.qml:4:5: error: Required property outside of a delegate
    required property int a

      this is yelling at me as the required property is not inside delegate, but in big qt, this syntax should be allowed.

      here is the code with big qt 6.6:

      // MyComponent.qml
import QtQuick
import QtQuick.Window
Text {
    required property int a
    Item {    }
}

// RequiredExperimentBigQt.qml <-- main qml file
import QtQuick
import QtQuick.Window
Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
    MyComponent {
    }
}

      the build didn't emit an error but i got a runtime error:

      11:55:40: Starting C:\Users\81808\Downloads\build-RequiredExperimentBigQt-Desktop_Qt_6_6_0_MinGW_64_bit-Debug\appRequiredExperimentBigQt.exe...
QQmlApplicationEngine failed to create component
qrc:/RequiredExperimentBigQt/MyComponent.qml:5:5: Required property a was not initialized
QML debugging is enabled. Only use this in a safe environment.

      by the way, even when i initialized the required property like this in the mcu project:

      import QtQuick
Rectangle {
    MyComponent {
        a: 1 // <--- initialize it
        anchors.centerIn: parent
        text: "Qt for MCUs"
    }
}

      i got this error:

      C:/Users/81808/Downloads/RequiredExperiment/RequiredExperiment.qml:5:9: error: Binding on read-only property
        a: 1

       

      i've checked the known issues and limitations of 2.6 but couldn't find this issue.

      https://doc.qt.io/QtForMCUs-2.6/qtul-known-issues.html

       

      both projects are attached to this ticket.

       

       

      Attachments

        Issue Links

          mentioned in

          Page Loading...

          No reviews matched the request. Check your Options in the drop-down menu of this sections header.

          Activity

            People

              k0rahman Karim Abdelrahman
              mikio_hirai Mikio Hirai
              Votes:
              0 Vote for this issue
              Watchers:
              2 Start watching this issue

              Dates

                Created:
                Updated:
                Resolved:

                Gerrit Reviews

                  There are no open Gerrit changes