Drawing half-circles with CoreGraphics - ios

Question

I know how to draw lines and shapes with CGPaths . But I couldn't figure out how to draw this symbol for a circuit diagram
What code should I write to get that half circle shape?
This is what I have so far:
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 5.0);
CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
CGContextMoveToPoint(context, 60, 80);
CGContextAddLineToPoint(context, 120, 80);
CGContextMoveToPoint(context, 120, 80);
CGContextAddArc(120,80,M_PI,M_PI/2);
CGContextMoveToPoint(context, 200, 80);
CGContextAddLineToPoint(context, 300, 80);
CGContextStrokePath(context);
}

Answer 1

You could create a UIBezierPath, e.g. something like:
UIBezierPath *path = [UIBezierPath bezierPath];
CGPoint point = CGPointMake(0, 50);
CGFloat radius = 15.0;
CGFloat lineLength = 25.0;
[path moveToPoint:point];
point.x += lineLength;
[path addLineToPoint:point];
point.x += radius;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2 clockwise:YES];
point.x += radius * 2;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2 clockwise:YES];
point.x += radius * 2;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2 clockwise:YES];
point.x += radius * 2;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2 clockwise:YES];
point.x += lineLength + radius;
[path addLineToPoint:point];
You could have your view controller just create a CAShapeLayer and add it to your view's layer.
CAShapeLayer *layer = [CAShapeLayer layer];
layer.path = [path CGPath];
layer.lineWidth = 2.0;
layer.fillColor = [[UIColor clearColor] CGColor];
layer.strokeColor = [[UIColor blackColor] CGColor];
[self.view.layer addSublayer:layer];
If you wanted to do it in the drawRect of a UIView subclass you could, stroke this path:
- (void)drawRect:(CGRect)rect
{
UIBezierPath *path = [UIBezierPath bezierPath];
CGPoint point = CGPointMake(0, 50);
CGFloat radius = 20.0;
CGFloat lineLength = 45.0;
[path moveToPoint:point];
point.x += lineLength;
[path addLineToPoint:point];
point.x += radius;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2.0 clockwise:YES];
point.x += radius * 2.0;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2.0 clockwise:YES];
point.x += radius * 2.0;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2.0 clockwise:YES];
point.x += radius * 2.0;
[path addArcWithCenter:point radius:radius startAngle:M_PI endAngle:M_PI * 2.0 clockwise:YES];
point.x += lineLength + radius;
[path addLineToPoint:point];
path.lineWidth = 2.0;
[[UIColor blackColor] setStroke];
[[UIColor clearColor] setFill];
[path stroke];
}
Or, as your revised question suggests, if you're more comfortable with CoreGraphics, you could do that, too:
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGPoint point = CGPointMake(0, 50);
CGFloat radius = 20.0;
CGFloat lineLength = 45.0;
CGContextMoveToPoint(context, point.x, point.y);
point.x += lineLength;
CGContextAddLineToPoint(context, point.x, point.y);
point.x += radius;
CGContextAddArc(context, point.x, point.y, radius, M_PI, M_PI * 2.0, NO);
point.x += radius * 2.0;
CGContextAddArc(context, point.x, point.y, radius, M_PI, M_PI * 2.0, NO);
point.x += radius * 2.0;
CGContextAddArc(context, point.x, point.y, radius, M_PI, M_PI * 2.0, NO);
point.x += radius * 2.0;
CGContextAddArc(context, point.x, point.y, radius, M_PI, M_PI * 2.0, NO);
point.x += lineLength + radius;
CGContextAddLineToPoint(context, point.x, point.y);
CGContextSetStrokeColorWithColor(context, [[UIColor blackColor] CGColor]);
CGContextSetLineWidth(context, 2.0);
CGContextDrawPath(context, kCGPathStroke);
}