1、利用NSUserDefaults來傳值，這種方法只限於傳少量數據的情形：

比如你要傳一個float的值，在需要傳的時候用
[[NSUserDefaults standardUserDefaults] setFloat:float forKey::@"float"]
接收值的時候用
[[NSUserDefaults standardUserDefaults] floatForKey:@"float"]

2、NSNotificationCenter來傳值

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch * touch = [touches anyObject];
CGPoint point = [touch locationInView:self];
CGRect roundRect = [self rectNeedRefreshFromThisPoint:point];
mLastPoint = CGPointMake(-1, -1);

NSLog(@"%s: point(%f,%f)", __FUNCTION__, point.x, point.y);

[self addToCurrentLineWithPoint:point.x y:point.y];
[self endLine];
[self setNeedsDisplayInRect:roundRect];

NSNumber *pointX = [NSNumber numberWithFloat:point.x];
NSNumber *pointY = [NSNumber numberWithFloat:point.y];
NSDictionary *pointDict = [NSDictionary dictionaryWithObjectsAndKeys:pointX,@"pointX",pointY,@"pointY", nil];
[[NSNotificationCenter defaultCenter]postNotificationName:@"passTouchedEndPointMsg"object:self userInfo:pointDict];

}

在消息中心的函數：

[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(getTouchedPoint:)
name:@"passTouchedEndPointMsg"
object:nil];

- (void) getTouchedPoint:(NSNotification *)noti
{
NSDictionary *pointDict = [noti userInfo];
touchedEndPointX = [[pointDict objectForKey:@"pointX"] floatValue];
touchedEndPointY = [[pointDict objectForKey:@"pointY"] floatValue];
NSLog(@"%f:%f",touchedEndPointX,touchedEndPointY);
}

用消息來傳參數有下面幾點說法：object指的是發送者、在poseter端的userInfo裡面可以存放要傳的參數，必須為NSDictionary類型。在center端獲取這個dictionary類型用:[notification userInfo];來獲取