How do I create a round cornered UILabel on the iPhone?

For devices with iOS 7.1 or later, you need to add:

yourUILabel.layer.masksToBounds = YES;
yourUILabel.layer.cornerRadius = 8.0;

iOS 3.0 and later

iPhone OS 3.0 and later supports the cornerRadius property on the CALayer class. Every view has a CALayer instance that you can manipulate. This means you can get rounded corners in one line:

view.layer.cornerRadius = 8;

You will need to #import <QuartzCore/QuartzCore.h> and link to the QuartzCore framework to get access to CALayer's headers and properties.

Before iOS 3.0

One way to do it, which I used recently, is to create a UIView subclass which simply draws a rounded rectangle, and then make the UILabel or, in my case, UITextView, a subview inside of it. Specifically:

1. Create a UIView subclass and name it something like RoundRectView.
2. In RoundRectView's drawRect: method, draw a path around the bounds of the view using Core Graphics calls like CGContextAddLineToPoint() for the edges and and CGContextAddArcToPoint() for the rounded corners.
3. Create a UILabel instance and make it a subview of the RoundRectView.
4. Set the frame of the label to be a few pixels inset of the RoundRectView's bounds. (For example, label.frame = CGRectInset(roundRectView.bounds, 8, 8);)

You can place the RoundRectView on a view using Interface Builder if you create a generic UIView and then change its class using the inspector. You won't see the rectangle until you compile and run your app, but at least you'll be able to place the subview and connect it to outlets or actions if needed.