Transform not working - iphone

Question

I am trying to rotate an object around it's current position,
CGAffineTransform trans = CGAffineTransformMakeRotation(compass_heading );
trans = CGAffineTransformTranslate(trans, 0, 90);
sun_image.transform = trans;
But it has no effect and sun_image doesn't move!
But if I change it to this and translate on X axis it moves! What does this mean?
CGAffineTransform trans = CGAffineTransformMakeRotation(compass_heading );
trans = CGAffineTransformTranslate(trans, 90, 0);
sun_image.transform = trans;

Answer 1

Here is how you can rotate an object:
CGFloat rotation = M_PI_2;
CGAffineTransform currentTransform = sun_image.transform;
CGAffineTransform newTransform = CGAffineTransformRotate(currentTransform,rotation);
[sun_image setTransform:newTransform];
With CGAffineTransformTranslate you can move an object, so you must use CGAffineTransformRotate.
For location manager :
-(void) locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading
{
//set the anchorPoint as the lower right corner of the layer
sun_image.layer.anchorPoint = CGPointMake(1, 1);
[sun_image.layer setAffineTransform:CGAffineTransformMakeRotation(-1*newHeading.trueHeading*3.14159/180)];
}

Answer 2

I generally do this for translation transforms:
sun_image.transform = CGAffineTransformMakeTranslation(dx,dy);

Answer 3

First set center of your UIImageView with your view center property like bellow..
yourImageView.center = self.view.center;
after set GestureRecognizer like bellow..
UIRotationGestureRecognizer *rotationRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:#selector(rotate:)];
[rotationRecognizer setDelegate:self];
[yourImageView addGestureRecognizer:rotationRecognizer];
[rotationRecognizer release];
and then use this bellow method for rotate UIImageView
-(void)rotate:(id)sender
{
UIView *imgTempGest = [sender view];
if([(UIRotationGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded)
{
lastRotation = 0.0;
return;
}
CGFloat rotation = 0.0 - (lastRotation - [(UIRotationGestureRecognizer*)sender rotation]);
CGAffineTransform currentTransform = [(UIPinchGestureRecognizer*)sender view].transform;
CGAffineTransform newTransform = CGAffineTransformRotate(currentTransform,rotation);
[[(UIRotationGestureRecognizer*)sender view] setTransform:newTransform];
[imgTempGest setTransform:newTransform];
lastRotation = [(UIRotationGestureRecognizer*)sender rotation];
}
take lastRotation variable of CGFloat like bellow..
CGFloat lastRotation;