Question

I don’t really understand what this function is good for. Can someone explain that (maybe with some examples)?

Can I rotate an UIImageView object with this one?

Answer 1

CGAffineTransformMakeRotation is a constructor that creates you a rotation matrix, like CGPointMake, or NSMakePoint. Some functions requires you to pass in a transformation matrix like:

  void CGPathAddArc (    CGMutablePathRef path,    const CGAffineTransform *m,    CGFloat x,    CGFloat y,    CGFloat radius,    CGFloat startAngle,    CGFloat endAngle,    bool clockwise ); 

You can use UIGraphicsGetCurrentContext to get a CGContextRef and transform/rotate the context as you like.

UPDATE: You can directly change UIView’s transform. It is a property:
@property(nonatomic) CGAffineTransform transform.
Thanks to Brad for pointing this out.