Passing a block to the CADisplayLink displayLinkWithTarget: parameter. This allows for an animation to be fully contained within a single block (here, animation()), which can be inserted into any object it animates, and that has access to it

animation.m

void (^(^(^animation)(void))(ControlState))(void) = ^{
        static CGFloat starting_radius, ending_radius, radius_step, radius_val;
        return ^{
            starting_radius = radius;
            ending_radius   = CGRectGetMinX(control_view.layer.bounds);
            radius_step     = 0.0005; //(ending_radius - radius);
            radius_val      = starting_radius;
            void (^eventHandlerBlock)(void) = ^{
                radius_val += radius_step;
                for (CaptureDeviceConfigurationControlProperty property = CaptureDeviceConfigurationControlPropertyTorchLevel; property < CaptureDeviceConfigurationControlPropertyNone; property++) {
                    [bg(property)() setCenter:[[UIBezierPath bezierPathWithArcCenter:center_point radius:radius_val startAngle:degreesToRadians(CaptureDeviceConfigurationPropertyButtonAngle(property)) endAngle:degreesToRadians(CaptureDeviceConfigurationPropertyButtonAngle(property)) clockwise:FALSE] currentPoint]];
                }
                if (radius_val >= ending_radius)
                {
                    [display_link invalidate];
                    [display_link removeFromRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
                }
            };
            
            const NSUInteger frameInterval = (unsigned int)round(radius_max - radius_min);
            
            return ^ {
                [display_link invalidate];
                display_link = [CADisplayLink displayLinkWithTarget:eventHandlerBlock selector:@selector(invoke)];
                display_link.preferredFramesPerSecond = frameInterval;
                
                [display_link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
            };
        };
    };