using multithreading to log in in iphone?

Question

in my application i am using web services (restful webservice), any way the log in operation using one service to authenticate user, I have a UIButton with IBAction which will call the web service and here is the method that call this web service:

-(void)LogInMethod{
    NSString * password=passwordTextField.text;
    NSString * mobileNumber=MobileTextField.text;
    if (password.length==0 || mobileNumber.length==0) {
        if (mobileNumber.length==0) {
            [wrongNoteLable setText:@"please enter a valid mobile number"];
            [wrongNoteLable setHidden:NO];
        }
        else if (password.length==0){
            [wrongNoteLable setText:@"please enter a valid password"];
            [wrongNoteLable setHidden:NO];
        }
    }
    else{

        NSString*UrlString=[[NSString alloc]initWithFormat:@"http://192.168.1.1:8080/test2/eattel/customers/signin/%@/123/%@",mobileNumber,password];
        NSURL *url = [[NSURL alloc] initWithString:UrlString ];
        NSError *error = nil;
        NSStringEncoding encoding = 0;
        customerID =[[NSString alloc]initWithContentsOfURL:url encoding:encoding error:&error];
        if (customerID) {
            if (![customerID isEqualToString: @"-1"]) {
                [self performSegueWithIdentifier:@"toMainMenuViewController" sender:self];
                NSLog(@"customer loged in with ID :%@",customerID);
            }
            else if ([customerID isEqualToString:@"-1"]){
                [wrongNoteLable setText:@"neither mobile number or password is wrong"];
                [wrongNoteLable setHidden:NO];
                NSLog(@"customer tried to log in with wrong password or phone Number :%@",customerID);
            }
        }
        else{
            [wrongNoteLable setText:@"no connection to the server"];
            [wrongNoteLable setHidden:NO];
            NSLog(@"customer tried to log in but there is no server connection :%@",customerID);
        }
    }

   // NSLog([dispatch_get_main_queue() description])

}

and I am trying to call the previous method using a thread in the IBAction like this:

- (IBAction)signInAction:(id)sender {

    NSThread* myThread = [[NSThread alloc] initWithTarget:self
                                                 selector:@selector(LogInMethod)
                                                   object:nil];
    [myThread start];  // Actually create the thread


}

but I am having this error:

WebThreadLockFromAnyThread(bool), 0xa08cf60: Obtaining the web lock from a thread other than the main thread or the web thread. UIKit should not be called from a secondary thread.

Answer 1

This is actually not related to your network code at all. The issue is that you are trying to update your UI from a background thread... UIKit generally must be used on the main thread. The reason you are seeing WebThreadLockFromAnyThread is that some controls on some some versions of UIKit internally use webkit to draw themselves, so that is what they happened to name the lock.

You really want to refactor your code in order to separate out the UI updates from the URL loading (possibly using KVO or notifications to handle the updates). You can make the current code work by wrapping every context where you make UIKit calls in, but it is going to be pretty ugly (I didn't actually try to compile the thing below, but it should work):

-(void)LogInMethod{
    __block NSString * password;
    __block NSString * mobileNumber;

    dispatch_sync(dispatch_get_main_queue(), ^{
        password=passwordTextField.text;
        mobileNumber =MobileTextField.text;
    }

    if (password.length==0 || mobileNumber.length==0) {
        dispatch_async(dispatch_get_main_queue(), ^{
            if (mobileNumber.length==0) {
                [wrongNoteLable setText:@"please enter a valid mobile number"];
                [wrongNoteLable setHidden:NO];
            }
            else if (password.length==0){
                [wrongNoteLable setText:@"please enter a valid password"];
                [wrongNoteLable setHidden:NO];
            }
        });
    }
    else{

        NSString*UrlString=[[NSString alloc]initWithFormat:@"http://192.168.1.1:8080/test2/eattel/customers/signin/%@/123/%@",mobileNumber,password];
        NSURL *url = [[NSURL alloc] initWithString:UrlString ];
        NSError *error = nil;
        NSStringEncoding encoding = 0;
        customerID =[[NSString alloc]initWithContentsOfURL:url encoding:encoding error:&error];
        dispatch_async(dispatch_get_main_queue(), ^{
            if (customerID) {
                if (![customerID isEqualToString: @"-1"]) {
                    [self performSegueWithIdentifier:@"toMainMenuViewController" sender:self];
                    NSLog(@"customer loged in with ID :%@",customerID);
                }
                else if ([customerID isEqualToString:@"-1"]){
                    [wrongNoteLable setText:@"neither mobile number or password is wrong"];
                    [wrongNoteLable setHidden:NO];
                    NSLog(@"customer tried to log in with wrong password or phone Number :%@",customerID);
                }
            }
            else{
                [wrongNoteLable setText:@"no connection to the server"];
                [wrongNoteLable setHidden:NO];
                NSLog(@"customer tried to log in but there is no server connection :%@",customerID);
            }
        });
    }

   // NSLog([dispatch_get_main_queue() description])

}



  //Update UI control.
});