Question

在延迟5秒后点击按钮后，数组中的总值将被执行。

- (IBAction)testButton:(id)sender {
NSArray *array = [NSArray arrayWithObjects:
                      @"Hefeweizen", @"IPA", @"Pilsner", @"Stout", nil];


for (NSIndexPath *anIndexPath in array) {




        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 5 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{


             NSLog(@"INDEX PATH %@",anIndexPath);



        }); 
}

如何为数组内的每个值创建5秒（给定）的延迟？

Answer 1

当您遍历数组时，您的dispatch_after（）调用将在非常短的时间内发生，因此它们的NSLog（）块将在几乎同时执行。

根据您要实现的目标和所需的精度，您可以做一些简单的事情，比如在迭代数组时5秒后安排每个块：

int64_t interval = 0;
for (NSIndexPath *anIndexPath in array) {
    dispatch_time_t start = DISPATCH_TIME_NOW;
    interval += 5;
    dispatch_after(dispatch_time(start, interval * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
        NSLog(@"INDEX PATH %@",anIndexPath);
    }); 
}

在这个例子中，第一个区块将在5秒内安排，第二个区块将在10秒内安排，第三个区块将在15秒内安排，依此类推。

Answer 2

您可以轻松地逐个排队执行：

- (void)executeFirstInArray:(NSArray *)array {
   NSString *firstItem = [array firstObject];
   array = [array subarrayWithRange:NSMakeRange(1, array.count - 1)];

   NSLog(@"Item: %@", firstItem);

   if (array.count > 0) {
      [self performSelector:_cmd withObject:array afterDelay:5.0];
   }
}

- (IBAction)testButton:(id)sender {
    NSArray *array = [NSArray arrayWithObjects:
                   @"Hefeweizen", @"IPA", @"Pilsner", @"Stout", nil];

   [self performSelector:@selector(executeFirstInArray:) withObject:array afterDelay:5.0];
}

Answer 3

试试这段代码，我添加了一个递增延迟，但我不确定这是否是一种健康的方法。无论如何，小循环应该不是问题：

- (IBAction)testButton:(id)sender {
    NSArray *array = [NSArray arrayWithObjects:
                      @"Hefeweizen", @"IPA", @"Pilsner", @"Stout", nil];

    int64_t delayInSeconds = 5.0;

    for (NSIndexPath *anIndexPath in array)
    {

        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);

        dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
            NSLog(@"INDEX PATH %@",anIndexPath);
        });
        delayInSeconds += 5;
    }
}

循环中所有值的延迟

3 个答案: