iOS: dragGesture don't move element - ios

Question

In my app I have this code to drag an object
I set my gesture:
UILongPressGestureRecognizer *downwardGesture = [[UILongPressGestureRecognizer new] initWithTarget:self action:#selector(dragGestureChanged:)];
downwardGesture.minimumPressDuration = 0.2;
[grid_element addGestureRecognizer:downwardGesture];
for (UILongPressGestureRecognizer *gestureRecognizer in self.view.gestureRecognizers)
{
[gestureRecognizer requireGestureRecognizerToFail:downwardGesture];
}
and in my method:
- (void) dragGestureChanged:(UILongPressGestureRecognizer*)gesture{
UIImageView *imageToMove;
CGPoint pointInSelfView;
if (gesture.state == UIGestureRecognizerStateBegan)
{
dragging = TRUE;
CGPoint location = [gesture locationInView:grid_element];
NSIndexPath *selectedIndexPath = [grid_element indexPathForItemAtPoint:location];
if (selectedIndexPath==nil) {
dragging = FALSE;
return;
}
indexToHide = selectedIndexPath.row;
imageToMove = [[UIImageView alloc]initWithImage:[UIImage imageNamed:#"image_1.png"]];
[self.view addSubview:imageToMove];
pointInSelfView = [gesture locationInView:self.view];
[imageToMove setCenter:pointInSelfView];
}
else if (gesture.state == UIGestureRecognizerStateChanged)
{
pointInSelfView = [gesture locationInView:self.view];
[imageToMove setCenter:pointInSelfView];
}
else if (gesture.state == UIGestureRecognizerStateEnded ||
gesture.state == UIGestureRecognizerStateCancelled ||
gesture.state == UIGestureRecognizerStateFailed)
{
dragging = FALSE;
}
}
it work in UIGestureRecognizerStateBegan, then imageToMove is added in self.view in the correct position but imageToMove don't drag in UIGestureRecognizerStateChanged; I show a NSLog for pointInSelfView in UIGestureRecognizerStateChanged and it changes correctly; where is the problem?
EDIT
if I use imageToMove as IBOutlet it work fine, but I don't understand the difference.

Answer 1

If you are using ARC, the iOS system is releasing object-imageToMove.
Creating a property with retain attribute, makes system retains the object and hence it moves.
The only thing I am confused is why there is no error in [imageToMove setCenter:pointInSelfView];. There should be an error saying - message is sent to deallocated instance. But I am pretty sure that the problem is due to memory release of imageToMove.