Share a simple way to implement basic drawing board functions under iOS

#import "" 
 
@implementation TouchView 
@synthesize points, points_all, paint_clr; 
 
- (id)initWithFrame:(CGRect)frame 
{ 
    self = [super initWithFrame:frame]; 
    if (self) { 
        // Initialization code 
        paint_clr = [UIColor greenColor]; 
    } 
    return self; 
} 
 
// Only override drawRect: if you perform custom drawing. 
// An empty implementation adversely affects performance during animation. 
- (void)drawRect:(CGRect)rect 
{ 
    // Drawing code 
    if ((!) || ( < 2)) { 
        return; 
    } 
       
    context = UIGraphicsGetCurrentContext(); 
//Set the brush thickness
    CGContextSetLineWidth(context, 5.0f); 
//Set the brush color
    //[[UIColor blueColor]set ]; 
    // [paint_clr set]; 
    //CGContextSetStrokeColorWithColor(context, [[UIColor blueColor]CGColor]); 
    CGContextSetStrokeColorWithColor(context, [paint_clr CGColor]); 
     
//Draw the previous trajectory
    for (int j = 0 ; j < [self.points_all count]; j++) { 
        NSMutableArray *points_tmp = [points_all objectAtIndex:j]; 
             
            for (int i = 0;i < [points_tmp count]-1;i++) 
            { 
                CGPoint point1 = [[points_tmp objectAtIndex:i] CGPointValue]; 
                CGPoint point2 = [[points_tmp objectAtIndex:(i+1)] CGPointValue]; 
                CGContextMoveToPoint(context, , ); 
                CGContextAddLineToPoint(context, , ); 
                CGContextStrokePath(context); 
            } 
        } 
     
//Draw this time
    for (int i=0; i < [ count]-1; i++) { 
        CGPoint point1 = [[ objectAtIndex:i] CGPointValue]; 
        CGPoint point2 = [[ objectAtIndex:(i+1)] CGPointValue]; 
        CGContextMoveToPoint(context, , ); 
        CGContextAddLineToPoint(context, , ); 
        CGContextStrokePath(context); 
    }     
} 
 
//Multi-touch is not supported
- (BOOL) isMultipleTouchEnabled 
{ 
    return NO; 
} 
 
//Create an array and record the initial ponit
- (void) touchesBegan:(NSSet *) touches withEvent:(UIEvent *) event 
{ 
    = [NSMutableArray array]; 
    CGPoint pt = [[touches anyObject] locationInView:self]; 
    [ addObject:[NSValue valueWithCGPoint:pt]]; 
} 
 
//Click these points during the movement
//Calling setNeedsDisplay will trigger the call of the drawRect method.
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    CGPoint pt = [[touches anyObject] locationInView:self]; 
    [ addObject:[NSValue valueWithCGPoint:pt]]; 
    [self setNeedsDisplay]; 
} 
 
- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    NSMutableArray *points_tmp = [[NSMutableArray alloc] initWithArray:]; 
    if (self.points_all == nil) { 
        self.points_all = [[NSArray alloc] initWithObjects:points_tmp, nil]; 
    }else { 
        self.points_all = [self.points_all arrayByAddingObject:points_tmp]; 
    } 
} 
@end