Set Text of an UILabel after dismissViewController in other Class - ios

Question

I haven't found a similar question that could answer my question.
My Question is: Why can't I access a UILabel from another class after the dissmissViewController?
Here is my Code:
ClassA.h:
#interface ClassA : UIViewController {
UILabel *_ErrorLabel;
UIActivityIndicatorView *_acIn1;
}
#property (weak, nonatomic) IBOutlet UILabel *ErrorLabel;
#property (weak, nonatomic) IBOutlet UIActivityIndicatorView *acIn1;
ClassA.m:
shouldPerformSegue, prepareForSegue and statusBarStyle Methods
ClassB.h:
- (IBAction)dismiss;
ClassB.m:
- (IBAction)dismiss
{
[self dismissViewControllerAnimated:YES completion:^{
ClassA *login = [[ClassA alloc] init];
[[login ErrorLabel] setText:#"Please use login."];
[[login acIn1] stopAnimating];
[[login acIn1] setHidesWhenStopped:YES];
[[login acIn1] setHidden:YES];
}];
}
Here is my Code I really hope somebody can help me: I AM ABOUT TO GIVE UP I DON'T KNOW WHY THIS WON'T WORK!
Thanks for your help.
~Markus
Edit1:
I have a ViewController ClassA that contains two text fields and when you click on login you come to a TabBarController where one tab contains the ClassB ViewController and in the ClassB ViewController there is a logout button --> dismiss and when you click this button you should come to the ClassA ViewController AND the ErrorLabel Text should change.
Complete Class: A --> LoginViewControler.h
#import <UIKit/UIKit.h>
#import "ShowProfileViewController.h"
#interface LoginViewController : UIViewController <ShowProfileViewControllerDelegate> {
UILabel *_ErrorLabel;
UIActivityIndicatorView *_acIn1;
}
#property (weak, nonatomic) IBOutlet UITextField *usernameTextField;
#property (weak, nonatomic) IBOutlet UITextField *passwordTextField;
#property (weak, nonatomic) IBOutlet UILabel *ErrorLabel;
#property (weak, nonatomic) IBOutlet UIActivityIndicatorView *acIn1;
#end
Complete Class: A --> LoginViewController.m
#import "LoginViewController.h"
#import "NewsNavigationController.h"
#import "TabViewController.h"
#interface LoginViewController () <UITextFieldDelegate>
#end
#implementation LoginViewController
#synthesize usernameTextField;
#synthesize passwordTextField;
#synthesize ErrorLabel;
#synthesize acIn1;
- (void)viewDidLoad
{
[super viewDidLoad];
[usernameTextField setDelegate:self];
[passwordTextField setDelegate:self];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}
- (UIStatusBarStyle)preferredStatusBarStyle
{
return UIStatusBarStyleLightContent;
}
- (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender
{
if([identifier isEqualToString:#"login"])
{
[acIn1 startAnimating];
[acIn1 setHidden:NO];
if([self login]){
return YES;
} else {
[self showErrorMessage:#"Data not correct!"];
[acIn1 stopAnimating];
[acIn1 setHidesWhenStopped:YES];
[acIn1 setHidden:YES];
return NO;
}
}
else {
[acIn1 stopAnimating];
[acIn1 setHidesWhenStopped:YES];
[acIn1 setHidden:YES];
return NO;
}
}
- (void)showErrorMessage:(NSString *)message
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error!"
message:message
delegate:self
cancelButtonTitle:#"OK"
otherButtonTitles:nil];
[alert show];
}
- (BOOL)login
{
NSString *usernameS = usernameTextField.text;
NSString *passwordS = passwordTextField.text;
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"http://localhost:8888/login.php?username=%#&password=%#", usernameS, passwordS]]];
NSDictionary *jsonDictionary = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSDictionary *loginDic = [jsonDictionary objectForKey:#"login"];
NSString *ErrorString = [loginDic objectForKey:#"returnString"];
NSLog(#"[+] Login: %#", ErrorString);
if ([ErrorString isEqualToString:#"Success"]){
ErrorLabel.text = #"Login";
return YES;
}
else {
ErrorLabel.text = ErrorString;
return NO;
}
}
- (void)didDismissViewController
{
[ErrorLabel setText:#"Bitte benutzen Sie den Login."];
[acIn1 stopAnimating];
[acIn1 setHidesWhenStopped:YES];
[acIn1 setHidden:YES];
}
- (void)prepareForSegue:(UIStoryboardSegue *)inSegue sender:(id)inSender
{
if([inSegue.identifier isEqualToString:#"login"])
{
ShowProfileViewController *vc = [[ShowProfileViewController alloc] init];
vc.delegate = self;
TabViewController *tabViewController = inSegue.destinationViewController;
NewsNavigationController *theController = [[tabViewController viewControllers] objectAtIndex:0];
[self presentViewController:vc animated:YES completion:nil];
}
}
#end
Complete Class: B --> ShowProfileViewController.h
#import <UIKit/UIKit.h>
#protocol ShowProfileViewControllerDelegate
- (void)didDismissViewController;
#end
#interface ShowProfileViewController : UIViewController
#property (nonatomic, assign) id<ShowProfileViewControllerDelegate> delegate;
- (IBAction)dismiss;
#end
Complete Class: B --> ShowProfileViewController.m
#import "ShowProfileViewController.h"
#import "LoginViewController.h"
#interface ShowProfileViewController ()
#end
#implementation ShowProfileViewController
- (void)viewDidLoad
{
[super viewDidLoad];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}
-(BOOL) textFieldShouldReturn:(UITextField *)textField{
[textField resignFirstResponder];
return YES;
}
- (void)viewWillAppear:(BOOL)inAnimated
{
[super viewWillAppear:inAnimated];
}
- (IBAction)dismiss
{
[self dismissViewControllerAnimated:YES completion:^{
[self.delegate didDismissViewController];
}];
}
#end

Answer 1

This doesn't work because inside your completion block, you're creating a new instance of your LoginViewController, and setting its text. What you should be actually doing is setting the text of the existing LoginViewController, that should appear after dismissing ShowProfileViewController
In order to achieve your desired behaviour, you can use the delegation pattern. If you're not familiar with this technique, it'd be very important to learn. It's is used all over the place in iOS and Mac OS X development.
The code below might require some tweaking on your side.
In ShowProfileViewController.h, add before #interface:
#protocol ShowProfileViewControllerDelegate
- (void)didDismissViewController
#end
Also, add the following property declaration to ShowProfileViewController:
#property (nonatomic, assign) id<ShowProfileViewControllerDelegate> delegate;
Then, change LoginViewController.h so it looks like
#import "ShowProfileViewController.h"
#interface LoginViewController : UIViewController <ShowProfileViewControllerDelegate> {
UILabel *_ErrorLabel;
UIActivityIndicatorView *_acIn1;
}
#property (weak, nonatomic) IBOutlet UILabel *ErrorLabel;
#property (weak, nonatomic) IBOutlet UIActivityIndicatorView *acIn1;
Now, in ShowProfileViewController.m, replace the code in the dismiss method so it looks like the following:
- (IBAction)dismiss
{
[self dismissViewControllerAnimated:YES completion:^{
[self.delegate didDismissViewController];
}];
}
In LoginViewController.m, add the following method:
- (void)didDismissViewController
{
[[self ErrorLabel] setText:#"Please use login."];
[[self acIn1] stopAnimating];
[[self acIn1] setHidesWhenStopped:YES];
[[self acIn1] setHidden:YES];
}
And finally, you need to set the delegate property in you ShowProfileViewController to point to the LoginViewController instance. Find in LoginViewController.m in which part of your code you create and present the ShowProfileViewController View Controller and set the delegate property to self. If you're using storyboards, you should do it inside prepareForSegue:.

Answer 2

ClassA *login = [[ClassA alloc] init];
is creating a completly new instance.Not the one you used for coming to class B