Change a UILabel's text from another class - iphone

Question

I have a view controller and a class (I am using storyboards). How can I change the text of a UILabel (in the view controller) from the class? I have tried this, but to no avail:
ViewController *mainView = [[ViewController alloc] init];
[mainView view];
[mainView.progressBar setProgress:integer animated:YES];
NSLog(#"Updated Progress Bar");
NSString *progressLabelText = [NSString stringWithFormat:#"%# out of %i followers", userString, [self.followers count]];
[mainView.progressLabel setText:progressLabelText];
NSLog(#"Updated Progress Label Text: %#", progressLabelText);
The text does not change using this code. What should I be doing instead?
Edit: The progressbar and label in the ViewController's .h file look like this:
#property (nonatomic, strong) IBOutlet UIProgressView *progressBar;
#property (nonatomic, strong) IBOutlet UILabel *progressLabel;
And they are fully linked up in Interface Builder.

Answer 1

Use delegate for messaging between classes or viewcontrollers.
Refer The Basics of Protocols and Delegates link.

Answer 2

Try to use Notification for updating the Lable text.
in your viewController write this:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(updateLabel) name:#"lblUpdate" object:nil];
and selector is :
-(void)updateLabel
{
self.lblObject.text = #"Your updated text"
}
and now in your Class call this using Post notification:
[[NSNotificationCenter defaultCenter] postNotificationName:#"lblUpdate" object:nil];
remember use same notification name "lblUpdate"

Answer 3

just property synthesize the string and then set that string in viewWillAppear: method of ViewController.m class
just take NSString variable in ViewController.h file like bellow..
#property (nonatomic, retain) NSString *progressText;
and synthesize this in ViewController.m file like bellow..
#synthesize progressText;
after that in viewDidLoad: method just set text at starting to the progressLableText like bellow...
- (void)viewDidLoad
{
progressText = #"Your Text";
[progressLabel setText:progressText];
}
and also in viewWillAppear: set the text like above...
- (void)viewWillAppear:(BOOL)animated
{
[progressLabel setText:progressText];
}
and in your code just change something like bellow..
ViewController *mainView = [[ViewController alloc] init];
[mainView view];
[mainView.progressBar setProgress:integer animated:YES];
NSLog(#"Updated Progress Bar");
NSString *progressLabelText = [NSString stringWithFormat:#"%# out of %i followers", userString, [self.followers count]];
mainView.progressText = progressLabelText;
[mainView.progressText retain];
NSLog(#"Updated Progress Label Text: %#", progressLabelText);
i hope this helpful to you...

Answer 4

But use a delegate to do the callbacks.
In your spamchecker.h add:
#protocol SpamCheckerDelegate <NSObject>
-(void)updateText:(NSString*)newText;
#end
#property (nonatomic, weak) id <SpamCheckerDelegate> delegate;
In your spamchecker.m where you need it add:
[self.delegate updateText:#"newText"];
Then in your mainView.h add:
#interface MainView : UIViewController <SpamCheckerDelegate>
In your mainview.m add:
spamchecker.delegate = self;
And implement the method like:
-(void)updateText:(NSString*)newText
{
[self.progressLabel setText:progressLabelText];
}