Draw lines with centers without them overlap - iphone

Question

I have a problem when i try to join lines. Here is a picture:
and I like that it looks like this:
and my code is:
- (void) drawRect:(CGRect)rect {
[super drawRect:rect];
CGContextRef context = UIGraphicsGetCurrentContext();
const CGFloat *components = CGColorGetComponents(self.lineColor.CGColor);
CGFloat red;
CGFloat green;
CGFloat blue;
CGFloat alpha;
if(CGColorGetNumberOfComponents(self.lineColor.CGColor) == 2)
{
red = 1;
green = 1;
blue = 1;
alpha = 1;
}
else
{
red = components[0];
green = components[1];
blue = components[2];
alpha = components[3];
if (alpha <= 0) alpha = 1;
}
// set the stroke color and width
CGContextSetRGBStrokeColor(context, red, green, blue, alpha);
CGContextSetLineWidth(context, 2.0);
if (self.points.count >0) {
BezierPoint *firstPoint = [self.points objectAtIndex:0];
CGContextMoveToPoint(context, firstPoint.center.x, firstPoint.center.y);
int index = 0;
for (BezierPoint *point in self.points ) {
if(index == 0){
index++;
continue;
}
CGContextAddLineToPoint(context, point.center.x, point.center.y);
}
CGContextAddLineToPoint(context, firstPoint.center.x, firstPoint.center.y);
}
CGContextSetRGBFillColor(context, 0.0, 0.0, 0.0, 0.0);
CGContextDrawPath(context, kCGPathFillStroke);
}
the problem I have is that for every point you add, the lines overlap and I would like that as I stay I add points for geometric figure that globulins do not overlap
If anyone can help me I will thank!!

Answer 1

I would move the logic that determines the order the lines are drawn to your view controller, and access the data needed to draw the view with from a delegate using a protocol. Views should not own their data. For example, in your .h try something like;
#import <UIKit/UIKit.h>
#protocol CowDrawViewDataSource
-(NSArray *) pointsToDraw;
#end
#interface CowDrawView : UIView
#property (nonatomic , weak) id <CowDrawViewDataSource> dataSource;
#end
Then, (and I hope this does answer you question) in the view controller, you set as your views delegate, construct the
-(NSArray *) pointsToDraw;
method, in such a way, to send your array of points in an order in from which they can be drawn. Say by finding the point the top/left point, then the top/right, then bottom/right, bottom/left. (although such an approach might not work so well with irregular polygons, and shapes that are contiguous, but not polygons.)
After you figure out how to get the array in the order you want, you can get it in your drawRect by sending a message to it's delegate such as
NSArray *points = [self.dataSource pointToDraw];
with little re-work in the drawRect it's self.

Answer 2

The easy way to correct your problem is first draw only single line segments between two points and see the results. Then you can form loops. I guess you are not assigning perfect coordinates points or your loop must consist of :
CGContextAddLineToPoint(context, point.center.x, point.center.y);
And then,
CGContextMoveToPoint(context, point.center.x, point.center.y);
This shows that first draw line and move to next point.
Hope this helps.