I’ve often seen people using a view’s layer to create a rounded corner or dropshadow. Something like this:

[v.layer setCornerRadius:30.0f];
[v.layer setBorderColor:[UIColor lightGrayColor].CGColor];
[v.layer setBorderWidth:1.5f];
[v.layer setShadowColor:[UIColor blackColor].CGColor];
[v.layer setShadowOpacity:0.8];
[v.layer setShadowRadius:3.0];
[v.layer setShadowOffset:CGSizeMake(2.0, 2.0)];

This has a HUGE performance impact, especially with the shadow. Putting views like this in a UITableView (or matter fact anything that moves) will create an android-ish scrolling experience, you do not want that. If you need to animate or move the view, avoid creating rounded corners or drop shadows like this!

Meet Core Graphics

I’ve created a simple UIView subclass to show you how to achieve the same result in a slightly different way. It uses Core Graphics to draw the view and in contrast to the code above, it will not result in a sluggish scrolling.

Here’s the drawing code:

- (void)drawRect:(CGRect)rect
{
    CGContextRef ref = UIGraphicsGetCurrentContext();
    
    /* We can only draw inside our view, so we need to inset the actual 'rounded content' */
    CGRect contentRect = CGRectInset(rect, _shadowRadius, _shadowRadius);
    
    /* Create the rounded path and fill it */
    UIBezierPath *roundedPath = [UIBezierPath bezierPathWithRoundedRect:contentRect cornerRadius:_cornerRadius];
    CGContextSetFillColorWithColor(ref, _fillColor.CGColor);
    CGContextSetShadowWithColor(ref, CGSizeMake(0.0, 0.0), _shadowRadius, _shadowColor.CGColor);
    [roundedPath fill];
    
    /* Draw a subtle white line at the top of the view */
    [roundedPath addClip];
    CGContextSetStrokeColorWithColor(ref, [UIColor colorWithWhite:1.0 alpha:0.6].CGColor);
    CGContextSetBlendMode(ref, kCGBlendModeOverlay);
    
    CGContextMoveToPoint(ref, CGRectGetMinX(contentRect), CGRectGetMinY(contentRect)+0.5);
    CGContextAddLineToPoint(ref, CGRectGetMaxX(contentRect), CGRectGetMinY(contentRect)+0.5);
    CGContextStrokePath(ref);
}