objective-c create and stroke an arc with CG - core-graphics

Question

I was following a Ray Wenderlich tutorial on creating arcs:
http://www.raywenderlich.com/33193/core-graphics-tutorial-arcs-and-paths
-what I am looking to do is begin at point a (a fixed point) and locate where the user touches the screen, if it is + point A, then I want to draw an arc to that point. Though I don't return any errors I also don't get the path to be stroked. Could someone review the code below and see what I am doing wrong?
#implementation KIP_Arc
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
- (void) setArc {
//set the frame
float frameX = _startPoint.x;
float frameY = _startPoint.y;
float frameW = _endPoint.x;
float frameH = 50.0;
[self setFrame:CGRectMake(frameX, frameY, frameW, frameH)];
self.backgroundColor = [UIColor clearColor];
}
- (BOOL)isFlipped {
return YES;
}
- (void)drawRect:(CGRect)rect {
[[UIColor blackColor] set];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGRect arcRect = self.frame;
CGMutablePathRef arcPath = [self createArcPathFromBottomOfRect:arcRect:25.0];
CGContextAddPath(context, arcPath);
CGContextClip(context);
CGContextFillPath(context);
CGContextRestoreGState(context);
CFRelease(arcPath);
}
- (CGMutablePathRef) createArcPathFromBottomOfRect : (CGRect) rect : (CGFloat) arcHeight {
CGRect arcRect = CGRectMake(rect.origin.x, rect.origin.y + rect.size.height - arcHeight, rect.size.width, arcHeight);
CGFloat arcRadius = (arcRect.size.height/2) + (pow(arcRect.size.width, 2) / (8*arcRect.size.height));
CGPoint arcCenter = CGPointMake(arcRect.origin.x + arcRect.size.width/2, arcRect.origin.y + arcRadius);
CGFloat angle = acos(arcRect.size.width / (2*arcRadius));
CGFloat startAngle = radians(180) + angle;
CGFloat endAngle = radians(360) - angle;
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddArc(path, NULL, arcCenter.x, arcCenter.y, arcRadius, startAngle, endAngle, 0);
CGPathAddLineToPoint(path, NULL, CGRectGetMaxX(rect), CGRectGetMinY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetMinX(rect), CGRectGetMaxY(rect));
return path;
}
static inline double radians (double degrees){
return degrees * M_PI/180;
}

Answer 1

CGContextClip, as a side effect, empties the current path. When you call CGContextFillPath immediately afterward, the current path is empty, so you fill nothing.
As its name implies, CGContextFillPath restricts itself to the context's current path. (If it didn't, its name would just be CGContextFill.) So, you don't need to clip.
Drop the CGContextClip call and just use CGContextFillPath.