Question

I just started to learn iOS programming and I have a problem with inheritance. There are 2 files.

First file

Header

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController {
    UILabel *myLabel;
}
@property (nonatomic, retain) IBOutlet UILabel *myLabel;
@end

Implementation:

#import "ViewController.h"
#import "NewClass.h"
@implementation ViewController
@synthesize myLabel;
#pragma mark - View lifecycle
- (void)viewDidLoad {
    [super viewDidLoad];
    myLabel.text = @"ViewController text!";    
    NewClass *myClass = [[[NewClass alloc] init] autorelease];
    [myClass setLabelText];
}
@end

Second file

Header:

#import "ViewController.h"
@interface NewClass : ViewController 
-(void) setLabelText ;
@end

Implementation:

#import "NewClass.h"
@implementation NewClass
- (void) setLabelText {
    myLabel.text = @"NewClass text!";
}
-(id)init { 
    self = [super init];                                       
    if (self != nil) {                                         
    }
    return self;                           
}
@end

And i set myLabel outlet in IB.

Why when i call [myClass setLabelText]; nothing happens? There also remained “ViewController text!” on label view.
Where is my problem? How can i change ViewController::myLabel.text in NewClass

Answer 1

This is not inheritance that you are doing. In your ViewController implementation, you have the following code

 NewClass *myClass = [[[NewClass alloc] init] autorelease];
[myClass setLabelText];

This is just creating an instance of the class NewClass and setting the labelText on that instance. You are never displaying it or adding it to a view.