CoreGraphics - clipping an inner circle (used in reference to a Stack Overflow question: http://stackoverflow.com/questions/18614376/calayer-clip-cgcontextaddarc-making-a-donut-slide-pie-chart

gistfile1.m

- (void)drawRect:(CGRect)rect {
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path addArcWithCenter:CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds)) radius:CGRectGetHeight(self.bounds) startAngle:0 endAngle:2.0*M_PI clockwise:YES];
    [path addArcWithCenter:CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds)) radius:100 startAngle:0 endAngle:2.0*M_PI clockwise:NO];
    [path addClip];
    
    
    self.layer.cornerRadius = 10.0;
    CGFloat colors[12] = {
        0.1, 0.18, 0.54, 1.0,
        0.38, 0.44, 0.65, 1.0,
        0.1, 0.18, 0.54, 1.0
    };
    CGFloat colorStops[3] = {0.0, 0.5, 1.0};
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace,
                                                                 colors,
                                                                 colorStops,
                                                                 3);
    CGColorSpaceRelease(colorSpace);
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextDrawRadialGradient(ctx, gradient, CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds)), 100, CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds)), CGRectGetHeight(self.bounds)/2, 1);
}