Add eraser tool after draw paint - iphone

Question

I have paint app. When i click button it launch paint view than user can paint. After i come back then click button the paintview won't reset. How can i reset a view in button click after draw pain.
code:
- (BOOL) initContext:(CGSize)size {
int bitmapByteCount;
int bitmapBytesPerRow;
// Declare the number of bytes per row. Each pixel in the bitmap in this
// example is represented by 4 bytes; 8 bits each of red, green, blue, and
// alpha.
bitmapBytesPerRow = (size.width * 4);
bitmapByteCount = (bitmapBytesPerRow * size.height);
// Allocate memory for image data. This is the destination in memory
// where any drawing to the bitmap context will be rendered.
cacheBitmap = malloc( bitmapByteCount );
if (cacheBitmap == NULL){
return NO;
}
cacheContext = CGBitmapContextCreate (cacheBitmap, size.width, size.height, 8, bitmapBytesPerRow, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaNoneSkipFirst);
return YES;
}
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
[self drawToCache:touch];
[self setNeedsDisplay];
}
- (void) drawToCache:(UITouch*)touch {
hue += 0.005;
if(hue > 1.0) hue = 0.0;
UIColor *color = [UIColor colorWithHue:hue saturation:0.7 brightness:1.0 alpha:1.0];
CGContextSetStrokeColorWithColor(cacheContext, [color CGColor]);
CGContextSetLineCap(cacheContext, kCGLineCapRound);
CGContextSetLineWidth(cacheContext, 15);
CGPoint lastPoint = [touch previousLocationInView:self];
CGPoint newPoint = [touch locationInView:self];
CGContextMoveToPoint(cacheContext, lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(cacheContext, newPoint.x, newPoint.y);
CGContextStrokePath(cacheContext);
CGRect dirtyPoint1 = CGRectMake(lastPoint.x-10, lastPoint.y-10, 20, 20);
CGRect dirtyPoint2 = CGRectMake(newPoint.x-10, newPoint.y-10, 20, 20);
[self setNeedsDisplayInRect:CGRectUnion(dirtyPoint1, dirtyPoint2)];
}
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
// Drawing code
CGContextRef context = UIGraphicsGetCurrentContext();
CGImageRef cacheImage = CGBitmapContextCreateImage(cacheContext);
CGContextDrawImage(context, self.bounds, cacheImage);
CGImageRelease(cacheImage);
}
In viewcontroller code:
PaintView *paint = [[PaintView alloc] initWithFrame:self.view.bounds];
[self.view addSubview:paint];
[paint release];

Answer 1

in touches moved,,,
make a toggle for eraser and change the code as follows.
if(togleEraser == NO)
{
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 0.0, 1.0);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
}
else
{
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 20);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1, 0, 0, 10);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextClearRect (UIGraphicsGetCurrentContext(), CGRectMake(lastPoint.x, lastPoint.y, 50, 50));
}