import QtQml import TestTypes QtObject { property var seq: SequenceTypeExample { id: mySequence } property int length: mySequence.qrealListProperty.length function goodSequenceWrite() { var someData = [1.1, 2.2, 3.3] someData.length = 100; for (var i = 0; i < 5; ++i) { for (var j = 0; j < 100; ++j) { someData[j] = j; } //Modifies entire sequence at once by copying a temp variable mySequence.qrealListProperty = someData; } } Component.onCompleted: goodSequenceWrite() }