title: Trying to use CGContextAddArc... nothing is drawn?
body: <p>I am trying to draw an arc. But nothing is drawn?</p>
  
  <pre><code>- (void)viewDidLoad {
      [super viewDidLoad];
      CGRect rect = CGRectMake(0,0,340,480);  
      UIView *ui = [[UIView alloc] initWithFrame:rect];
      [self.view addSubview:ui];
      CGContextRef context = UIGraphicsGetCurrentContext(); 
      CGContextAddArc(context, 50, 50, 20, 0, 30, 0); 
  }
  </code></pre>