A rect type has x, y, width and height attributes.
For example, to read the Item::childrenRect rect property:
Rectangle {
width: childrenRect.width
height: childrenRect.height
Rectangle { width: 100; height: 100 }
}
To create a rect value, specify it as a "x, y, width x height" string:
CustomObject { myRectProperty: "50,50,100x100" }
Or use the Qt.rect() function:
CustomObject { myRectProperty: Qt.rect(50, 50, 100, 100) }
See also QML Basic Types.