Double negation for 'enabled-prop' of an Action - why?

rengel

In the Qt Documentation for 'Action QML Type', the property 'enabled' has the value

enabled: (!!activeFocusItem && !!activeFocusItem["cut"])

context:

Action {
    id: cutAction
    text: "Cu&t"
    shortcut: StandardKey.Cut
    iconName: "edit-cut"
    enabled: (!!activeFocusItem && !!activeFocusItem["cut"])
    onTriggered: activeFocusItem.cut()
}

Why does the value use two double negations? Are they required? If so, why?
Is this just a JavaScrip 'trick' for a more elaborate expression?
If I remove these double negations, the code works as well.

sierdzio

Yes this is a JavaScript thing. It will treat all false-like states as false (undefined, false, 0, null, etc.). More info https://stackoverflow.com/questions/784929/what-is-the-not-not-operator-in-javascript

rengel

Thanks! That helped. I'm using PyCharm with the QML plugin. This plugin flags (falsely) the double negation as a syntax error. I have posted this error on the QML Support webpage of JetBrains.