#import
                "
                DrawingView.h
                "
                @interface
                 DrawingView ()

@property (nonatomic, strong) UIBezierPath *path;

@end@implementation DrawingView

- (void)awakeFromNib
{
    //create a mutable path
    self.path = [[UIBezierPath alloc] init];
    self.path.lineJoinStyle = kCGLineJoinRound;
    self.path.lineCapStyle = kCGLineCapRound;
    ?
    self.path.lineWidth = 5;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    //get the starting point
    CGPoint point = [[touches anyObject] locationInView:self];

    //move the path drawing cursor to the starting point    [self.path moveToPoint:point];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    //get the current point
    CGPoint point = [[touches anyObject] locationInView:self];

    //add a new line segment to our path    [self.path addLineToPoint:point];

    //redraw the view    [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect
{
    //draw path    [[UIColor clearColor] setFill];
    [[UIColor redColor] setStroke];
    [self.path stroke];
}
@end

                #import
                "
                DrawingView.h
                "
                #import <QuartzCore/QuartzCore.h>

@interface DrawingView ()

@property (nonatomic, strong) UIBezierPath *path;

@end
?
@implementation DrawingView

+ (Class)layerClass
{
    //this makes our view create a CAShapeLayer
    //instead of a CALayer for its backing layerreturn [CAShapeLayer class];
}

- (void)awakeFromNib
{
    //create a mutable path
    self.path = [[UIBezierPath alloc] init];

    //configure the layer
    CAShapeLayer *shapeLayer = (CAShapeLayer *)self.layer;
    shapeLayer.strokeColor = [UIColor redColor].CGColor;
    shapeLayer.fillColor = [UIColor clearColor].CGColor;
    shapeLayer.lineJoin = kCALineJoinRound;
    shapeLayer.lineCap = kCALineCapRound;
    shapeLayer.lineWidth = 5;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    //get the starting point
    CGPoint point = [[touches anyObject] locationInView:self];

    //move the path drawing cursor to the starting point    [self.path moveToPoint:point];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    //get the current point
    CGPoint point = [[touches anyObject] locationInView:self];

    //add a new line segment to our path    [self.path addLineToPoint:point];

    //update the layer with a copy of the path
    ((CAShapeLayer *)self.layer).path = self.path.CGPath;
}
@end

                #import
                "
                DrawingView.h
                "
                #import <QuartzCore/QuartzCore.h>
#define BRUSH_SIZE 32

@interface DrawingView ()

@property (nonatomic, strong) NSMutableArray *strokes;

@end@implementation DrawingView

- (void)awakeFromNib
{
    //create array
    self.strokes = [NSMutableArray array];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    //get the starting point
    CGPoint point = [[touches anyObject] locationInView:self];

    //add brush stroke    [self addBrushStrokeAtPoint:point];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    //get the touch point
    CGPoint point = [[touches anyObject] locationInView:self];

    //add brush stroke    [self addBrushStrokeAtPoint:point];
}

- (void)addBrushStrokeAtPoint:(CGPoint)point
{
    //add brush stroke to array    [self.strokes addObject:[NSValue valueWithCGPoint:point]];

    //needs redraw    [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect
{
    //redraw strokesfor (NSValue *value in self.strokes) {
        //get point
        CGPoint point = [value CGPointValue];

        //get brush rect
        CGRect brushRect = CGRectMake(point.x - BRUSH_SIZE/2, point.y - BRUSH_SIZE/2, BRUSH_SIZE, BRUSH_SIZE);

        //draw brush stroke    ?
        [[UIImage imageNamed:@"Chalk.png"] drawInRect:brushRect];
    }
}
@end

- (void)addBrushStrokeAtPoint:(CGPoint)point
{
    //add brush stroke to array    [self.strokes addObject:[NSValue valueWithCGPoint:point]];

    //set dirty rect    [self setNeedsDisplayInRect:[self brushRectForPoint:point]];
}

- (CGRect)brushRectForPoint:(CGPoint)point
{
    return CGRectMake(point.x - BRUSH_SIZE/2, point.y - BRUSH_SIZE/2, BRUSH_SIZE, BRUSH_SIZE);
}

- (void)drawRect:(CGRect)rect
{
    //redraw strokesfor (NSValue *value in self.strokes) {
        //get point
        CGPoint point = [value CGPointValue];

        //get brush rect
        CGRect brushRect = [self brushRectForPoint:point];
        ?
        //only draw brush stroke if it intersects dirty rectif (CGRectIntersectsRect(rect, brushRect)) {
            //draw brush stroke
            [[UIImage imageNamed:@"Chalk.png"] drawInRect:brushRect];
        }
    }
}