Error :crash my app -[__NSArrayI objectAtIndex:]: index 3 beyond bounds [0 .. 2]'

Question

我已经创建了一个测验应用程序。但是会产生一些问题，我的问题是 myarray 在我的应用程序崩溃后完成。

我想在打开 UIAlertView 后完成 myarray。怎么可能请帮助。谢谢

// int _currentTitle;
// _currentTitle=0;
// NSArray* myarray;

 - (void)viewDidLoad {
[super viewDidLoad];

myarray = [NSArray arrayWithObjects: @"Jill Valentine", @"Peter Griffin", @"Meg Griffin", nil];
  }


- (IBAction)changeque:(id)sender {
[self changequestion];
}

-(void)changequestion
{
NSString *str = myarray[_currentTitle++];
questionLabel.text = str;


//        if (_currentTitle == myarray.count) { //reload myarray 
//            _currentTitle = 0;
//        }

}

Answer 1

myarray 有 3 个元素，跨越形式

myarray[0] = "Jill Valentine"

,

myarray[1] = "Peter Griffin"

和

myarray[2] = "Meg Griffin"

在 Obj-C 中，您使用 nil 值终止数组，因此 myarray[3] 不包含任何值。但是，当 _currentTitle 达到该值时，您的代码不会显示。

Answer 2

您需要某种条件来检查 _currentTitle 是否等于 [myarray count]。当满足此条件时，调用一个显示警报视图的方法。

示例可以是 -

-(void)changequestion
{

     if (_currentTitle >= [myarray count]) {
          // call method to present alert view
          [self noMoreQuestions];     
     }
     else {
     NSString *str = myarray[_currentTitle];
     questionLabel.text = str;
     }
     _currentTitle++; // this is done last so question at index 0 happens
}

-(void)noMoreQuestions {
     // present alert to user
     UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Alert" message:@"Your array count has finished" preferredStyle:UIAlertControllerStyleAlert];

     UIAlertAction *ok = [UIAlertAction  actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {
                   }];

     UIAlertAction *cancel = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {
                   }];

     [alert addAction:ok];
     [alert addAction:cancel];
     [self presentViewController:alert animated:YES completion:nil];
     // remember to reset _currentTitle to 0 before starting next quiz
}

Answer 3

把这个：

-(void)changequestion
{
if (_currentTitle == myarray.count) { //reload myarray 
         _currentTitle = 0;
     }
NSString *str = myarray[_currentTitle++];
questionLabel.text = str;

}

Error :crash my app -[__NSArrayI objectAtIndex:]: index 3 beyond bounds [0 .. 2]'

Error :crash my app -[__NSArrayI objectAtIndex:]: index 3 beyond bounds [0 .. 2]'

iphone

objective-c

nsarray

ios