Change the font size and font style of UISearchBar iOS 7

Try this, It's Working Fine for iOS 5.0 and up: (iOS 7 also)

- (void)viewDidLoad
{

[[UITextField appearanceWhenContainedIn:[UISearchBar class], nil] setFont:[UIFont fontWithName:@"Helvetica" size:20]];

}

For iOS 8

- (void)viewDidLoad
    {

[[UITextField appearanceWhenContainedIn:[UISearchBar class], nil] setDefaultTextAttributes:@{
            NSFontAttributeName: [UIFont fontWithName:@"Helvetica" size:20],
      }];

    }

The accepted answer did not work for me on iOS 7.1. I had to change it to this:

[[UITextField appearanceWhenContainedIn:[UISearchBar class], nil] setDefaultTextAttributes:@{
            NSFontAttributeName: [UIFont fontWithName:@"Avenir-Heavy" size:20.],
}];