为什么我的应用程序没有添加10s位置？

Question

我在网上关注了一个教程，我终于想出了如何让它发挥作用。唯一的缺点是，它只会添加一个位置，然后按下10次按钮才能再次使用。

这是我的代码：

ViewController.h:

@interface ViewController :UIViewController {
int counter;
IBOutlet UILabel *count;
}
-(IBAction)minus;
-(IBAction)plus;
-(IBAction)zero;
@end

And ViewController.m:

@implementation ViewController
-(IBAction)plus {
counter=counter + 1;
count.text = [NSString stringWithFormat:@"%i",counter];
}
-(IBAction)minus {
counter=counter - 1;
count.text = [NSString stringWithFormat:@"%i",counter];
}
-(IBAction)zero {
counter=0;
count.text = [NSString stringWithFormat:@"%i",counter];
}
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
counter=0;
count.text = @"0";
[super viewDidLoad];
}
@end

有关详细信息，请参阅我的视频：https://www.youtube.com/watch?v=P3yhtPHsc-4&feature=youtu.be