Iboutlet connected yet Still says it's null

I'm new at iPhone development and was practicing a bit. I connected a uilabel I made through IB to an IBOutlet in my code as many tutorials said but upon trying to set text of it it's still saying it's null? I defined the IBOutlet object on 开发者_JS百科my .h class and connected it fine through IB without a problem but idk why it's still null. Any help would be greatly appreciated.

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Okay, first things first, let's remove some of the extraneous stuff and focus on the core of what you need.

#import "CalculatorBrain.h"

@interface CalculatorViewController : UIViewController 
{
    CalculatorBrain* _calculatorModel;
    UILabel *display;
}

- (IBAction) digitPressed:(UIButton *)sender;

@property (nonatomic, retain) IBOutlet UILabel *display;

@end


#import "CalculatorViewController.h"

@implementation CalculatorViewController
@synthesize display;

- (void)dealloc
{
    [display release], display = nil;
    [_calculatorModel release];
    [super dealloc];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    if (! _calculatorModel)
    {
        _calculatorModel = [[CalculatorBrain alloc] init];
    }
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    NSLog(@"display is: %@", display);
}

- (IBAction)digitPressed:(UIButton *)sender
{
    NSString *currentDigit = [[sender titleLabel] text];
    [display setText:[NSString stringWithFormat:@"%@", currentDigit]];
}

@end

Let us know what happens when you've set the label (display) and the action (digitPressed:) in InterfaceBuilder.

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Try changing your property to copy (or retain, but copy is more idiomatic for this situation):

@property (copy) IBOutlet UILabel *display;

Your assign property is not incrementing the reference count for the string, thus there is no guarantee that it will still exist by the time you need it.