ios - 更新 dispatch_sync 队列中的 UI (activityIndi​​cator)( Objective-C )

Question

这是我的登录按钮:

- (IBAction)signInButtonAction:(id)sender
{
    if ([self.phoneNumberTextField.text length] == 0 || [self.passwordTextField.text length] == 0) {
        [self initializeAlertControllerForOneButtonWithTitle:@"Alert!" withMessage:kEmptyTextFieldAlertMSG withYesButtonTitle:@"Ok" withYesButtonAction:nil];

    } else {
        if ([self alreadyRegisteredPhoneNumber] == YES) {
            if ([self.password isEqualToString:self.passwordTextField.text]) {
                [self goToHomeViewController];

            } else {
                [self initializeAlertControllerForOneButtonWithTitle:@"Wrong Password!" withMessage:kWrongPasswordMSG withYesButtonTitle:@"Ok" withYesButtonAction:nil];

            }

        } else {
            [self initializeAlertControllerForOneButtonWithTitle:@"Alert!" withMessage:kSignInPhoneNumberDoesnotExistMSG withYesButtonTitle:@"Ok" withYesButtonAction:nil];
        }
    }
}

这是我的 alreadyRegisteredPhoneNumber 方法，我只是在其中检查给定的电话号码是否已注册。

- (BOOL)alreadyRegisteredPhoneNumber
{
    [self.activityIndicator startAnimating];
    __block BOOL isThisPhoneNumberRegistered = NO;

    BlockWeakSelf weakSelf = self;
    SignInViewController *strongSelf = weakSelf;

    dispatch_sync(dispatch_queue_create("mySyncQueue", NULL), ^{
        NSString *PhoneNumberWithIsoCountryCode = [NSString stringWithFormat:@"%@%@", strongSelf.countryCode, strongSelf.phoneNumberTextField.text];
        strongSelf.userModelClass = [[RetrieveDataClass class] retrieveUserInfoForPhoneNumber:PhoneNumberWithIsoCountryCode];
        if ([strongSelf.userModelClass.phone_number length] != 0) {
            strongSelf.phoneNumber = strongSelf.userModelClass.phone_number;
            strongSelf.password = strongSelf.userModelClass.password;
            isThisPhoneNumberRegistered = YES;
            [strongSelf.activityIndicator stopAnimating];
        }
    });

    return isThisPhoneNumberRegistered;
}

使用此方法时，问题是当我按下 Sign In 按钮时 activityIndi​​cator 没有出现。否则它会以同步方式工作，这是完美的。

activityIndi​​cator 没有出现的原因是我必须更新 dispatch_async(dispatch_get_main_queue() 中与 UI 相关的更改(或者不是？？)。但是如果我重新安排我的像这样的代码:

- (BOOL)alreadyRegisteredPhoneNumber
{
    [self.activityIndicator startAnimating];
    __block BOOL isThisPhoneNumberRegistered = NO;

    BlockWeakSelf weakSelf = self;
    SignInViewController *strongSelf = weakSelf;

    dispatch_async(dispatch_get_main_queue(), ^{

        dispatch_sync(dispatch_queue_create("mySyncQueue", NULL), ^{
            NSString *PhoneNumberWithIsoCountryCode = [NSString stringWithFormat:@"%@%@", strongSelf.countryCode, strongSelf.phoneNumberTextField.text];
            strongSelf.userModelClass = [[RetrieveDataClass class] retrieveUserInfoForPhoneNumber:PhoneNumberWithIsoCountryCode];
            if ([strongSelf.userModelClass.phone_number length] != 0) {
                strongSelf.phoneNumber = strongSelf.userModelClass.phone_number;
                strongSelf.password = strongSelf.userModelClass.password;
                isThisPhoneNumberRegistered = YES;
                [strongSelf.activityIndicator stopAnimating];
            }
        });
    });

    return isThisPhoneNumberRegistered;
}

activityIndi​​cator 显示完美，但它总是返回 isThisPhoneNumberRegistered = NO，因为它以异步方式工作，其中我的更新 isThisPhoneNumberRegistered = YES最近回来。

所以如果我愿意，这个场景:

1. 用户按下登录按钮
2. 然后显示 activityIndi​​cator
3. 我的服务器调用 (strongSelf.userModelClass = [[RetrieveDataClass class] retrieveUserInfoForPhoneNumber:PhoneNumberWithIsoCountryCode];) 检索数据并设置 isThisPhoneNumberRegistered = YES 或 isThisPhoneNumberRegistered = NO 根据它

4. 然后将值返回给If else条件

   if ([self alreadyRegisteredPhoneNumber] == YES) {
           if ([self.password isEqualToString:self.passwordTextField.text]) {
               [self goToHomeViewController];
   
   } else {
               [self initializeAlertControllerForOneButtonWithTitle:@"Wrong Password!" withMessage:kWrongPasswordMSG withYesButtonTitle:@"Ok" withYesButtonAction:nil];
   
   }
   

我该怎么做？
非常感谢。

Answer 1

一般来说，您想要使用异步进程，这样您就可以“做其他事情”，例如更新 UI 以让用户知道正在发生的事情。

为了做到这一点，您需要分离您的逻辑。试着用这些术语来思考它:

signInButtonAction {
   if no phone or password entered
      show alert
   else
      showAnimatedSpinner()
      checkForRegisteredPhone()
}

checkForRegisteredPhone {
   // start your async check phone number process
   //  on return from the async call,
   if !registered
      hide spinner
      show kSignInPhoneNumberDoesnotExistMSG message
   else
      checkForMatchingPassword()
}

checkForMatchingPassword {
   if !passwordsMatch
      hide spinner
      show "passwords don't match" message
   else
      hide spinner
      goToHomeViewController
}

换句话说，不要编写代码，以免其“锁定”到进程中，从而阻止其他任何事情发生。