Scott Montgomerie Scott Montgomerie -4 years ago 134
Javascript Question

How to do a "is_a", "typeof" or instanceof in QML?

I want to run through a list of QML components and choose one type:

for (var i = 0; i < controls.children.length; ++i) {
if ( typeof (controls.children[i].height) == "QDeclarativeRectangle")
{
// do stuff
}
}


How does one accomplish this?

Answer Source

You can't use typeof for this directly because it will always return you 'object' as a type of any QML element. There are several alternatives however that you could use. One is setting the objectName of the each element to its type and check that in your loop or define a property and check for that property. This will require a bit more work but you could create your qml element that has this property and than use it wherever you need it. Here is a sample code:

Rectangle {
  id: main
  width: 300; height: 400

  Rectangle {
    id: testRect
    objectName: "rect"
    property int typeId: 1
  }

  Item {
    id: testItem
    objectName: "other"
  }

  Component.onCompleted: {
    for(var i = 0; i < main.children.length; ++i)
    {
        if(main.children[i].objectName === "rect")
        {
            console.log("got one rect")
        }
        else
        {
            console.log("non rect")
        }
    }
    for(i = 0; i < main.children.length; ++i)
    {
        if(main.children[i].typeId === 1)
        {
            console.log("got one rect")
        }
        else
        {
            console.log("non rect")
        }
    }
  }
}
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