IPhone对@selector的函数如何传参数 (nstimer)

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
if(oldView != nil){
[dict setObject:oldView forKey:@"oldView"];
}
if(newView != nil){
[dict setObject:newView forKey:@"newView"];
}
[NSTimer scheduledTimerWithTimeInterval:0.0 target:self selector:@selector(onTimer:) userInfo:dict repeats:NO];
[dict release];

- (void)onTimer:(NSTimer *)timer {
UIView *oldView = [[timer userInfo] objectForKey:@"oldView"];
UIView *newView = [[timer userInfo] objectForKey:@"newView"];
[UIView animateWithDuration:2.0 delay:0
options:UIViewAnimationOptionAllowUserInteraction
animations:^{
oldView.alpha = 0.0;
newView.alpha = 1.0;
}
}