ios - 如何防止后面的代码在 UIAlertController 中先执行

Question

我正在使用 shouldPrepareForSegue 方法，但我遇到了问题

__block BOOL Stat;

if([identifier isEqualToString:@"SignOut"]){
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Are You Sure?" message:@"" preferredStyle:UIAlertControllerStyleAlert];
        UIAlertAction *can = [UIAlertAction actionWithTitle:@"CANCEL" style:UIAlertActionStyleCancel handler:^(UIAlertAction *action){
            Stat = NO;
            [alert dismissViewControllerAnimated:YES completion:^{}];
        }];
        UIAlertAction *sign = [UIAlertAction actionWithTitle:@"SIGN OUT" style:UIAlertActionStyleDestructive handler:^(UIAlertAction *action){
            Stat = YES;
            NSLog(@"%d",Stat);
        }];

        [alert addAction:can];
        [alert addAction:sign];
        [self presentViewController:alert animated:YES completion:^{}];

    NSLog(@"%d",Stat);
    return Stat;

}else{
    return YES;
}

Stat 的值总是返回 0，因为它在我响应 UIAlertController 之前被执行，因为后面的代码首先被执行如何防止它。

Answer 1

你可以像下面这样创建一个带有完成 block 的函数，并在你需要的地方调用它并检查标志

- (void)signOutWithcompletionHandler:(void (^)(BOOL flag))completionHandler

if([identifier isEqualToString:@"SignOut"]){
  UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Are You Sure?" message:@"" preferredStyle:UIAlertControllerStyleAlert];
  UIAlertAction *can = [UIAlertAction actionWithTitle:@"CANCEL" style:UIAlertActionStyleCancel handler:^(UIAlertAction *action){
    completionHandler(NO);
    [alert dismissViewControllerAnimated:YES completion:^{}];
  }];
  UIAlertAction *sign = [UIAlertAction actionWithTitle:@"SIGN OUT" style:UIAlertActionStyleDestructive handler:^(UIAlertAction *action){
    completionHandler(YES);
    NSLog(@"%d",Stat);
  }];

  [alert addAction:can];
  [alert addAction:sign];
  [self presentViewController:alert animated:YES completion:^{}];
}else{
  completionHandler(YES);
}