How to allow users to draw throughout my app?

Question

I have implemented the following code which allows the user to draw on an imageView. I would like to implement this throughout my app but would prefer not to keep copying and pasting.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
pointCurrent = [touch locationInView:self.view];

}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint pointNext = [touch locationInView:self.view];
UIGraphicsBeginImageContext(drawImage.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)];
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, 0.0, 1.0);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), pointCurrent.x, pointCurrent.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), pointNext.x, pointNext.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
pointCurrent = pointNext;
}

So far I have tried to create a category but I'm unsure if this is the right way to go about it. Do I make a custom method and try to call that in the other classes or am I barking up the wrong tree? Thanks in advance for taking the time to read this question.

Answer 1

I modified your code a little, because I was getting that same error that you mention in your comment. This code worked for me.

@interface RDImageView ()
@property (nonatomic) CGPoint pointCurrent;
@end

@implementation RDImageView

-(instancetype)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super initWithCoder:aDecoder]) {
        self.userInteractionEnabled = YES;
        self.backgroundColor = [UIColor blueColor];
    }
    return self;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    self.pointCurrent = [touch locationInView:self];

}



- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint pointNext = [touch locationInView:self];
    UIGraphicsBeginImageContext(self.frame.size);
    [self.image drawInRect:self.bounds];
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1,1, 0.0, 1.0);
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), self.pointCurrent.x, self.pointCurrent.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), pointNext.x, pointNext.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    self.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    self.pointCurrent = pointNext;
}