What's the matter with this script? Detect object dragging with iPhone Touch

The script dosn't work, why?? I can't understand. The script should detect if an object is dragged or not and print it in the GUIText.

static var dragging : boolean = false; // contains true if the object is dragged

function Update() { for (var touch : Touch in Input.touches) { if (touch.phase == TouchPhase.Began) dragging = true; else if(touch.phase == TouchPhase.Ended) dragging = false; } var targetText = GameObject.FindWithTag("txt"); targetText.guiText.text = "is dragged = " + dragging; }