Objective-C: Calling class 2 instance from class1 [alloc init] way is not working

Question

I've got the following method on a GameScreen.m file, with its own declaration - (void) drawNumbers on a GameScreen.h file:

//GameScreen.h
#import <UIKit/UIKit.h>

@interface GameScreen : UIView
{
  IBOutlet UIButton *cell00;
}
- (void) drawNumbers;
- (IBAction) onCellClick:(id)sender;
@property (nonatomic, retain) IBOutlet UIButton *cell00;

@end



//GameScreen.m

#import "GameScreen.h"
- (void) drawNumbers
{
   //testing if this works, so far it doesn't
   [cell00 setTitle:@"Whatever" forState:UIControlStateNormal];
   [cell00 setTitle:@"Whatever" forState:UIControlStateHighlighted];
}

I'm trying to call this method from my GameScreenViewController.m file, this way:

//GameScreenViewController.m

#import "GameScreenViewController.h"
#import "GameScreen.h"
... 
- (void) viewDidLoad
{
   GameScreen *aGameScreen = [[GameScreen alloc] init];
   [aGameScreen drawNumbers];
   [aGameScreen release];

   [super viewDidLoad];
}

This is supposed to change the title of a button in a GameScreen.xib file where GameScreenViewController.m is the viewController and GameScreen class is the event handler where I get all the button clicks, timers running, etc. I am trying to call [drawNumbers] from [viewDidLoad] since I want the title to be changed when the screen is brought up front (screen management is done through the AppDelegate files).

The thing is, if I call drawNumbers instance from inside the same class through

//GameScreen.m

#import GameScreen.h
-(void) onButtonClick:(id)sender
{
    //some other code

    [self drawNumbers];
}

it works (as to say, nothing wrong with the code implementation or the graphic interface).

I've browsed through Apple Guide and tons of pages on the Internet, but I can't seem to find any light to this. Any further help (including answers as to where exactly find the answer in the ADG) would be really appreciated.

(Edited: here goes the AppDelegate code to flip to the specific view, just in case):

//myAppAppDelegate.h
#import <UIKit/UIKit.h>
@class myAppViewController, GameScreenViewController;
@interface myAppDelegate : NSObject <UIApplicationDelegate>
{
    UIWindow *window;
    myAppViewController *viewController;
    GameScreenViewController *gameScreenViewController;
}

- (void) flipToGameScreen;

@property (nonatomic, retain) UIWindow *window;
@property (nonatomic, retain) GameScreenViewController *gameScreenViewController;
@end

//myAppAppDelegate.m
-(void) flipToGameScreen
{
    GameScreenViewController *aGameScreenView = [[GameScreenViewController alloc] initWithNibName: @"GameScreen" bundle:nil];
    [self setGameScreenViewController:aGameScreenView];
    [aGameScreenView release];
    [gameScreenViewController.view.frame = [[UIScreen mainScreen] applicationFrame];
    [viewController.view removeFromSuperview];
    [self.window addSubview:[gameScreenViewController view]];
}

Answer 1

Since your cell00 is to be set by a NIB it will be nil if you simply do [[GameScreen alloc] init]. It will only be set if the corresponding NIB is loaded (and a connection is actually set up).

If the cell can be accessed in your viewDidLoad, create a property on GameScreen and pass it through the property (or a dedicated initWithCell: or something).

If you have something like an IBOutlet GameScreen *aGameScreen; on your GameScreenViewController (and also established a connection to cell00 in the same NIB) you should access that instead.