Max/Min Scale of Pinch Zoom in UIPinchGestureRecognizer - iPhone iOS

Question

How would I be able to limit the scale of the UIPinchGestureRecognizer to a min and max level? The scale property below seems to be relative to the last known scale (the de

Answer 1

Here is the solution that I figured out after using Anomie's answer as a starting point.

- (void)handlePinchGesture:(UIPinchGestureRecognizer *)gestureRecognizer {

    if([gestureRecognizer state] == UIGestureRecognizerStateBegan) {
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = [gestureRecognizer scale];
    }

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || 
        [gestureRecognizer state] == UIGestureRecognizerStateChanged) {

        CGFloat currentScale = [[[gestureRecognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];

        // Constants to adjust the max/min values of zoom
        const CGFloat kMaxScale = 2.0;
        const CGFloat kMinScale = 1.0;

        CGFloat newScale = 1 -  (lastScale - [gestureRecognizer scale]); 
        newScale = MIN(newScale, kMaxScale / currentScale);   
        newScale = MAX(newScale, kMinScale / currentScale);
        CGAffineTransform transform = CGAffineTransformScale([[gestureRecognizer view] transform], newScale, newScale);
        [gestureRecognizer view].transform = transform;

        lastScale = [gestureRecognizer scale];  // Store the previous scale factor for the next pinch gesture call  
    }
}