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QML Loader for variables ??



  • Trying to use a Loader to reload a variable every hour...
    Below is code used, getting error on property alias temp: myvar.temp
    ERROR ->Invalid alias reference. Unable to find id "myvar"

    why is the Loader variable not seen?
    any advice appreciated.

    QML CODE used:

    temp.qml - loader file // this file is updated every hour with latest weather temp

    code_text
    
    Item {
    id:myvar
    property string temp : " Clear - 85°"
    

    }

    main qml file
    ...

    code_text
    ```Item {
        Loader { 
            id: pageLoader 
            asynchronous: true
            source: "/run/media/hammer/Data/projects/temp.qml"
        }
        
              }
              
              Text {
                // property string temp : " Clear - 85°"
               property alias temp: myvar.temp // does not work
               property alias temp: pageLoader.temp  //also tried this same error??
               text: temp
               font.family: "Roboto"
               font.pointSize: 22
               color: "black"
           }
          }
    

    code_text



  • hi
    @mtaylor said in QML Loader for variables ??:

    use a Loader to reload a variable every hour...

    Loader is not used for that please see the description https://doc.qt.io/qt-5/qml-qtquick-loader.html#details

    You can use QML Timer



  • Any id is file scoped.

    So main.qml have no idea what is myvar.

    You can access to your variable via the loader item property (pageLoader.item.temp).



  • ok so that gets rid of the error using text: pageLoader.myvar.temp
    but nothing shows up on screen output??

    i am using qmlscene for testing is there another way to show the value of that variable?

    thanks



  • @LeLev
    i am working on one part at a time, trying to get loader working, then implement a timer to reload every hour, thanks i looked at docs already, but cant find an example of loading a property / variable,
    seems it should be easy, but not having any luck...



  • main.qml

    
    Window {
        visible: true
        width: 640
        height: 480
        title: qsTr("Hello World")
        Item {
            id: item
            property alias loaderEle: pageLoader
            Loader {
                id: pageLoader
                asynchronous: true
                source: "qrc:/temp.qml"
            }
        }
    
        Text {
            property alias temp2: item.loaderEle 
            text: temp2.item == null ? "" : temp2.item.temp
            font.family: "Roboto"
            font.pointSize: 22
            color: "black"
        }
    }
    

    temp.qml

    import QtQuick 2.0
    
    Item {
        id:myvar
        property string temp : " Clear - 85°"
    }
    
    

    Please make sure you have access to loader element. After that to access the properties from the loaded source in loader, use ".item"



  • @Yaswanth
    still get no output..

    what i did get working is this ...
    some how u can call files in the same directory so i tried this
    created a file called Temp.qml

    import QtQuick 2.0
    Item {
        id:myvar
    property string temp : " Clear - 85°"
    Text {
           text: temp
           font.family: "Roboto"
            font.pointSize: 22
            color: "black"
            antialiasing : true
          }
    }
    
    in main.qml
    ```...
    Temp {width:140;height:16;anchors.right: parent} // function call to Temp.qml
    

    works, but when i add a timer

    code_text
    ```
    Timer {
            interval: 5000 //5 sec //testing
            repeat: true
           running: true
           triggeredOnStart: true
           onTriggered: Temp {width:140;height:16;anchors.right: parent} // function call to Temp.qml
       }
    

    get this error -
    Cannot assign object type Temp_QMLTYPE_7 with no default method

    how can i call this Temp.qml function with a timer?

    thanks



  • @mtaylor said in QML Loader for variables ??:

    how can i call this Temp.qml function with a timer?

    What do you mean by calling Temp.qml?



  • @Yaswanth
    for the timer trigger -
    onTriggered: Temp {width:140;height:16;anchors.right: parent} // function call to Temp.qml

    am i right with the timer, that it executes that trigger line every 5 secs?

    without the timer the Temp {} function works fine...



  • @mtaylor
    The way which you have used onTriggered is incorrect.
    If you want to display or update Temp.qml properties, using id of the Temp.qml component, you can access.
    If you want to create Temp.qml,
    https://doc.qt.io/qt-5/qtqml-javascript-dynamicobjectcreation.html.
    To understand Timer usage, please check https://doc.qt.io/archives/qt-4.8/qml-timer.html#onTriggered-signal



  • @Yaswanth
    thanks i have read the docs,
    still not clear on what can executed with the timer trigger is reached??
    i am not updating Temp.qml, with qml code
    it is written by a separate JS script every hour...i want my main qml file to reload that file every hour to reflect the updated variable contents

    here is what i am trying to create - https://imgur.com/sAW05ez
    custom kscreenlocker app to show temperature and other items

    i can load the Temp.qml file by this Temp {} works fine in my test case

    but when i add the timer part with Temp {}

    onTriggered: Temp {width:140;height:16;anchors.right: parent} // function call to Temp.qml
    

    get this error -
    Cannot assign object type Temp_QMLTYPE_7 with no default method

    i guess the question is how do make this call with a timer?


  • Qt Champions 2019

    @mtaylor said in QML Loader for variables ??:

    onTriggered: Temp {width:140;height:16;anchors.right: parent}

    I'm not a QML expert, but don't you create an instance of Temp here instead of calling a method on existing instance?
    onTriggered expects something executable, not just an instance (without default method, so it can't be called).

    Don't you actually want to update an existing Temp instance? You should have one in the same QML file where onTrigger is.



  • @jsulm
    i believe i am in over my head here...i think what i am trying to do is not even possible...
    kscreenlocker does not allow internet access, and i think my idea of reloading a qml page every hour will not work due to the way kscreenlocker works.

    thanks for the help



  • @mtaylor said in QML Loader for variables ??:

    i believe i am in over my head here...i think what i am trying to do is not even possible...

    dude thats why i proposed you 1 houre Skype QML lesson in PM ..


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