间隔时间

@property (retain) NSDate *lockout;

- (void) report: (NSString *) aString
{
	// Only allow this method to run every five seconds
	if (!self.lockout) 
		self.lockout = [NSDate dateWithTimeIntervalSinceNow:5.0f];
	else if ([[NSDate date] timeIntervalSinceDate:self.lockout] < 0.0f) return;
	self.lockout = [NSDate dateWithTimeIntervalSinceNow:5.0f];
	
	// 每隔5秒执行下面代码
	[vs performSelector:@selector(startSpeakingString:) withObject:aString];
}

loading画面至少3秒

(void)showFeedbackViewWithType:(FeedbackViewType)type delegate:(id)delegate userInfo:(id)userInfo
{
self.aftertime = [NSDate dateWithTimeIntervalSinceNow:3];
}



- (void)hideFeedbackView
{
    NSDate *nowtime=[NSDate date];
    if ([[nowtime earlierDate:self.aftertime] isEqualToDate:nowtime]) {
//        [self performSelector:@selector(hideFeedbackViewLater) withObject:nil  afterDelay:1.0];
        [self hideFeedbackView];
    } else {
        [self hideFeedbackViewLater];
    }
    
}