Eraser for UIBezierPath - objective-c

Question

I am using UIBezierPath for free hand drawing in an iPad app. I want to apply an eraser to a uibezierpath.
However, I want to only erase the drawing in its path. I cannot use the path color as the background color because I have other elements on the background.
Below is how I am creating my free hand drawings:
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
self.backgroundColor = [UIColor clearColor];
self.opaque = NO;
lineWidths = 10;
brushPattern = [UIColor greenColor];
pathArray = [[NSMutableArray alloc]init];
bufferArray = [[NSMutableArray alloc]init];
self.multipleTouchEnabled = NO;
}
return self;
}
- (void)drawRect:(CGRect)rect {
for (NSMutableDictionary *dictionary in pathArray) {
UIBezierPath *_path = [dictionary objectForKey:#"Path"];
UIColor *_colors = [dictionary objectForKey:#"Colors"];
[_colors setStroke];
_path.lineCapStyle = kCGLineCapRound;
[_path stroke];
}
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
myPath = [[UIBezierPath alloc]init];
myPath.lineWidth = lineWidths;
CGPoint touchPoint = [[touches anyObject] locationInView:self];
UITouch *mytouch = [[touches allObjects] objectAtIndex:0];
[myPath moveToPoint:[mytouch locationInView:self]];
[myPath addLineToPoint:CGPointMake(touchPoint.x, touchPoint.y)];
dict = #{#"Path": myPath, #"Colors": brushPattern};
[pathArray addObject:dict];
[self setNeedsDisplay];
[undoManager registerUndoWithTarget:self selector:#selector(undoButtonClicked) object:nil];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *mytouch = [[touches allObjects] objectAtIndex:0];
[myPath addLineToPoint:[mytouch locationInView:self]];
[self setNeedsDisplay];
}

Answer 1

Store a BOOL value for erase: BOOL _erase;
BOOL eraseButtonIsTapped = ...
if eraseButtonIsTapped {
_erase = yes;
} else{
_erase = NO;
}
When drawing:
[myPath strokeWithBlendMode:_erase?kCGBlendModeClear:kCGBlendModeNormal alpha:1.0f];

Answer 2

Just try this
brushPattern = view.backgroundColor;
This will draw a new line with the color what exactly behind your drawn path. And you can use the same pathArray to do this. So that later on you can implement redo/undo operations too. if you want i could explain you more on this.