简单的游戏获得错误“线程1：信号SIGABRT

Question

它首先运行但后来又出现错误。这就是日志所说的

“2014-01-26 17：43：23.264更高或更低[26812：70b] * 由于未捕获的异常'NSUnknownKeyException'而终止应用程序，原因：'[setValue：forUndefinedKey：]：对于键输入，此类不符合键值编码。'“

#import "ViewController.h"

int answer = 0;
int guess = 0;
int turn = 0;



@interface ViewController ()

@end

@implementation ViewController


- (void)viewDidLoad; {

       [super viewDidLoad];
       _higher.hidden = YES;
       _lower.hidden = YES;
       answer = arc4random() % 100 + 1;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
       [_labelGuess resignFirstResponder];

}

- (void)didReceiveMemoryWarning
{
       [super didReceiveMemoryWarning];
       // Dispose of any resources that can be recreated.
}

- (IBAction)enterButton:(UIButton *)sender {

        NSString *input = _labelGuess.text;
        guess = [input intValue ];
        _labelGuess.text=input;

        if (guess > answer) {
            _lower.hidden = NO;
            _higher.hidden = NO;

    }
    else if (guess < answer) {
            _lower.hidden = YES;
            _higher.hidden = NO;
    }
    else {
            NSLog(@"Correct! The answer was %i", answer);
    }

        NSLog(@"The random value is %i", answer);
        scanf("%i", &guess);
}


@end

// HEADER FILE！

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@property (weak, nonatomic) IBOutlet UITextField *labelGuess;

@property (weak, nonatomic) IBOutlet UIImageView *chooseNumber;

@property (weak, nonatomic) IBOutlet UIImageView *higher;

@property (weak, nonatomic) IBOutlet UIImageView *lower;

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


@end