ios - 在等待上一个执行完成时循环遍历 block

Question

我有一个代码块，它循环遍历一个数组并对其执行 block 代码。目前它看起来像这样:

for (NSString *myString in myArray) {

    [self doSomethingToString:myString WithCompletion:^(BOOL completion) {
        string = [NSString stringByAppendingString:@"Test"];
    }];

}

我想等待上一个迭代完成，然后再开始下一个迭代。我如何循环遍历这样的 block 代码？

Answer 1

试试这个

    dispatch_semaphore_t sema = dispatch_semaphore_create(0);

    for (NSString *myString in myArray) {

        [self doSomethingToString:myString WithCompletion:^(BOOL completion) {
            string = [NSString stringByAppendingString:@"Test"];
            dispatch_semaphore_signal(sema);
        }];

        dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
        dispatch_release(sema);

    }