Ios 布尔方法的问题

我使用以下方法检查我的数据库中是否已存在电子邮件：

-(BOOL) emailHasBeenTaken:(NSString *)email
{



        PFQuery *query = [PFUser query];
        [query whereKey:@"email" equalTo:email];

        [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
            if (!error && objects.count>0) {
                NSLog(@"in the emailHasbeenTaken EMAIL IS DUPLICATE");
                [self duplicateEmail];

            } else
            {
                NSLog(@"in the emailHasBeenTaken, EMAIL IS NOT EXISTENT");
            }
        }];

    return YES;

}

我所面临的问题是，有时它会工作，有时它不会，我不确定我做错了什么，我所说的工作与否的意思是这。。。我检查新用户何时尝试使用以下代码注册：

     if (![self emailHasBeenTaken:self.emailTF.text]) {
    // EMAIL WAS NOT FOUND IN DATABASE SO IT WILL ASSIGN THE 
       TEXTFIELD VALUES TO USER PROPERTIES     

    email = self.emailTF.text;
                    user.email = email;
                } else
                {
                    [self duplicateEmail];
                    return;
                } 

---

我做错了什么？为什么我要添加

到我的if语句以获得所需的结果。。有没有一种方法可以从
BOOL
语句接收多个返回？i、 e.一个案例将返回YES，另一个案例将返回NO。
您总是返回
YES
首先，您正在进行一个异步调用来解析，该调用不起任何作用（除了调用
duplicateEmail
方法，您尚未发布该方法，因此我不知道该调用什么）然后您总是从您的
电子邮件hasbeentaken:
方法返回
YES

由于您需要进行异步调用以获取接收该电子邮件的任何用户，因此需要重新格式化方法的工作方式。您需要将其更改为以下内容：

- (void)emailHasBeenTaken:(NSString *)email completion:(void(^)(BOOL emailIsTaken, NSError *error))completionBlock
{
    void (^completionCopy)(BOOL, NSError *) = [completionBlock copy];

    PFQuery *query = [PFUser query];
    [query whereKey:@"email" equalTo:email];

    [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {

        if (error) {
            NSLog(@"in the emailHasbeenTaken ERROR HAS OCCURRED");
            if (completionCopy) {
                completionCopy(NO, error);
            }
            return;
        }

        if (objects.count > 0) {
            NSLog(@"in the emailHasbeenTaken EMAIL IS DUPLICATE");
            if (completionCopy) {
                completionCopy(YES, nil);
            }
        }
        else {
            NSLog(@"in the emailHasBeenTaken, EMAIL IS NOT EXISTENT");
            if (completionCopy) {
                completionCopy(NO, nil);
            }
        }
    }];
}

NSString *emailFromTextField = self.emailTF.text;

[self emailHasBeenTaken:emailFromTextField completion:^(BOOL emailIsTaken, NSError *error) {
    if (error) {
        // TODO: handle any errors here
        return;
    }

    if (!emailIsTaken) {
        // Assuming "email" and "user" are instance variables here:
        email = emailFromTextField;
        user.email = email;
    }
    else {
        [self duplicateEmail];
    }
}];

请注意，此方法本身现在是异步的，因此在
if
语句中将其用作条件是不可能的。您可以这样使用它：

- (void)emailHasBeenTaken:(NSString *)email completion:(void(^)(BOOL emailIsTaken, NSError *error))completionBlock
{
    void (^completionCopy)(BOOL, NSError *) = [completionBlock copy];

    PFQuery *query = [PFUser query];
    [query whereKey:@"email" equalTo:email];

    [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {

        if (error) {
            NSLog(@"in the emailHasbeenTaken ERROR HAS OCCURRED");
            if (completionCopy) {
                completionCopy(NO, error);
            }
            return;
        }

        if (objects.count > 0) {
            NSLog(@"in the emailHasbeenTaken EMAIL IS DUPLICATE");
            if (completionCopy) {
                completionCopy(YES, nil);
            }
        }
        else {
            NSLog(@"in the emailHasBeenTaken, EMAIL IS NOT EXISTENT");
            if (completionCopy) {
                completionCopy(NO, nil);
            }
        }
    }];
}

NSString *emailFromTextField = self.emailTF.text;

[self emailHasBeenTaken:emailFromTextField completion:^(BOOL emailIsTaken, NSError *error) {
    if (error) {
        // TODO: handle any errors here
        return;
    }

    if (!emailIsTaken) {
        // Assuming "email" and "user" are instance variables here:
        email = emailFromTextField;
        user.email = email;
    }
    else {
        [self duplicateEmail];
    }
}];

请你再详细解释一下，我的
duplicateEmail
方法所做的只是在我的视图中显示一个警报。当然，我会用我认为你应该做的事情更新我的答案。我尝试添加你的代码，但我得到一个生成错误“参数太多，无法阻止调用，预期为1，有2”@matt，我试过了，但是我一直得到一个构建失败的错误