gistfile1.txt

//
//  LHDFingerpaintView.m
//  Drawing
//
//  Created by Steven Masuch on 2014-07-31.
//  Copyright (c) 2014 Lighthouse Labs. All rights reserved.
//

#import "LHDFingerpaintView.h"

@interface LHDTouchPair : NSObject

@property (nonatomic) CGPoint touch1Point;
@property (nonatomic) CGPoint touch2Point;

@end

@implementation LHDTouchPair

@end

@interface LHDFingerpaintView ()

@property (nonatomic) NSMutableArray * touchPairs;

@end

@implementation LHDFingerpaintView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        _touchPairs = [NSMutableArray array];
    }
    return self;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    // We don't need to do anything here
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    // Here's the meat of this
    for (UITouch *touch in touches) {
        LHDTouchPair *touchPair = [[LHDTouchPair alloc] init];
        touchPair.touch1Point = [touch locationInView:self];
        touchPair.touch2Point = [touch previousLocationInView:self];
        [self.touchPairs addObject:touchPair];
    }
    
    [self setNeedsDisplay];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
    
}

- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
    CGContextSetLineWidth(context, 5.0);
    
    for (LHDTouchPair *pair in self.touchPairs) {
        CGContextBeginPath(context);
        CGContextMoveToPoint(context, pair.touch1Point.x, pair.touch1Point.y);
        CGContextAddLineToPoint(context, pair.touch2Point.x, pair.touch2Point.y);
        CGContextStrokePath(context);
    }
    
}

@end