CODEWITHSUNDEEP
qmlqtquick2
RvdK
RvdK

Reputation: 19800

Only set property conditionally in QML

I'm trying to set a property of a custom QML element conditionally. Meaning I only want to set it if something is true.

In this example I want to set someProperty when the application has a specific value, but if not, I want to let the object retain the original value. Also I want to let it behave like a binding. Meaning if the condition changes, it restores/sets the property again.

main.qml

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    MyObject {
        someProperty: (title == "different" ? "other_value" : 'undefined')
    }
}

MyObject.qml 

Rectangle {

    property var someProperty: "original_value"

    Component.onCompleted: {
        console.error("MyOject.someProperty: " + someProperty)
    }
}

So this prints:

qml: MyOject.someProperty: undefined

I want it to print

qml: MyOject.someProperty: original_value

So I have tried:

I don't want to use any onCompleted kind of syntax because I want to retain the binding and not litter my code.

Upvotes: 1

Views: 2119

Answers (2)

derM
derM

Reputation: 13711

You might use States together with PropertyChanges and set the State to be active, when the condition is met.

The State-System has the property that it saves restores the original state, once a Stateis left again.

Upvotes: 4

Kevin Krammer
Kevin Krammer

Reputation: 5207

You could try with a Binding element

MyObject {
    id: myObject
}

Binding {
    target: myObject
    property: "someProperty"
    value: "other_value"
    when: title == "different"
}

Upvotes: 1

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