Expression QML Type

(BETA) Evaluates JavaScript expressions. More...

• List of all members, including inherited members

Properties

• errorString : string
• expressionString : string
• isLiteralValue : bool
• literalValue : var
• notifyOnValueChange : bool
• scope : object
• script : QQmlScriptString
• text : string

Signals

• valueChanged()

Methods

• clear()
• object evaluate()

Detailed Description

The Expression component evaluates JavaScript expressions within a QML context.

The following code snippet evaluates the expression "a * b", where 'a' is counting up from 1 and 'b' is set to 1000. The code uses the PropertySet component to define the QML context where 'a' and 'b' are taken from, and you will get notifications of the expression changing because of either 'a' or 'b'.

Item {
    Label {
        id: results
    }

    Expression {
        id: expression
        onValueChanged: results.text = expression.evaluate();
    }

    PropertySet {
        id: propertySet
    }

    Timer {
        id: timer
        repeat: true
        interval: 1000
        onTriggered: propertySet.a++;
    }

    Component.onCompleted: {
        propertySet.a = 1;
        propertySet.b = 1000;
        expression.scope = propertySet;
        expression.text = "a * b";
        results.text = expression.evaluate();
        expression.notifyOnValueChange = true;
        timer.start();
    }
}

Property Documentation

Signal Documentation

Method Documentation