Problem Dev Cocoa textField

#import <Cocoa/Cocoa.h>

@interface AppDelegate : NSObject <NSApplicationDelegate>

{
    int fromValue;
    int toValue;
    int nombre;
    BOOL comptage;
}

@property (weak) IBOutlet NSTextField *champFrom;
@property (weak) IBOutlet NSTextField *champTo;
@property (weak) IBOutlet NSTextField *champAff;

- (IBAction)takeFrom:(id)sender;
- (IBAction)takeTo:(id)sender;

- (IBAction)start:(id)sender;
- (IBAction)stop:(id)sender;

- (void)updateUserInterface;
- (id) init;

@end

#import "AppDelegate.h"

@interface AppDelegate ()

@property (weak) IBOutlet NSWindow *window;

@end

@implementation AppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    // Insert code here to initialize your application
    [self init];
}
- (void)applicationWillTerminate:(NSNotification *)aNotification {
    // Insert code here to tear down your application
}

- (IBAction)takeFrom:(id)sender {
    fromValue = [sender intValue];
    //[self updateUserInterface];
}

- (IBAction)takeTo:(id)sender {
    toValue = [sender intValue];
    //[self updateUserInterface];
}

- (IBAction)start:(id)sender {
    nombre=fromValue;
    [self updateUserInterface];
    comptage=true;
    if ((fromValue<=toValue)&&(comptage==true)){
        while ((nombre<toValue)&&(comptage==true)) {
            nombre=nombre+1;
            [self updateUserInterface];
        }
    }
}

- (IBAction)stop:(id)sender {
    //nombre=toValue;
    comptage=false;
    [self updateUserInterface];
}

- (void)updateUserInterface {
    [self.champAff setIntValue:nombre];
}

- (id) init{
    self = [super init];
    if (self) {
        fromValue=0;
        toValue=0;
        nombre=0;
        comptage=true;
        return self;
    }
    else
        return nil;
}
@end