ios - 更新dispatch_sync队列中的UI(activityIndi​​cator)( objective-c )

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];
        }
    }
}

这是我已经注册的电话号码方法，在这里我只是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;
}

使用此方法的问题是，当我按“登录”按钮时，activityIndicator不会出现。否则它会以同步方式工作，这是完美的。

activityIndicator未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（或否？）。但是，如果我这样重新排列我的代码：

- (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;
}

activityIndicator显示完美，但是它总是返回isThisPhoneNumberRegistered = NO，因为它以异步方式工作，而我的更新isThisPhoneNumberRegistered = YES最近又返回了。

因此，如果需要，这种情况下：


用户按下登录按钮
然后出现activityIndicator
我的服务器调用（strongSelf.userModelClass = [[RetrieveDataClass class] retrieveUserInfoForPhoneNumber:PhoneNumberWithIsoCountryCode];）检索数据并根据其设置isThisPhoneNumberRegistered = YES或isThisPhoneNumberRegistered = NO
然后将值恢复为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。

最佳答案

通常，您希望使用Asynch进程，以便可以“做其他事情”，例如更新UI，以使用户知道发生了什么事情。

为此，您需要分离逻辑。尝试用以下术语来思考：

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，不要编写您的代码，这样它就会“锁定”在一个进程中，从而防止发生其他任何事情。