Hi All!
im new in objective C programming but i've read an excellent book by Steve.
well... my problem is that my frac calculator displays nothing. i was trying to find where is the problem can be and wrote little test program:

#import <UIKit/UIKit.h>

@interface SenderViewController : UIViewController {
	
	UILabel *display1;
	NSMutableString *aString;

}

@property(retain, nonatomic) IBOutlet UILabel *display1;
@property(retain, nonatomic) NSMutableString *aString;

-(IBAction)click1:(UIButton *) sender;

@end

#import "SenderViewController.h"

@implementation SenderViewController


@synthesize display1, aString;


-(IBAction)click1:(UIButton *) sender
{
		
	[aString appendFormat:@"%i",sender.tag];
	display1.text = aString;
}


- (void)dealloc 
{
	[display1 release];
	[super dealloc];
}

@end

this prog have button, display and should return tag button on display... but nothing happens. it is a simple analog of two methods from exercise 21.2:
-(void) processDigit: (int) digit & -(IBAction) clickDigit: (UIButton *) sender

can you give me some advices?!


i find my problem but dont know how to fix it. its all because displayString = null all time

-(void) processDigit: (int) digit;
{
	currentNumber = currentNumber * 10 + digit;
	[displayString appendString: [NSString stringWithFormat: @"%i", digit]];  //cannot assign displayString here...
	display.text = displayString;
	
}

dude thx u so much )))