iphone - 洗牌数组未捕获异常

Question

我使用四个按钮并打乱按钮标签值以在每次点击时查看不同的值，因为我从数组中显示按钮的值，当我试图打乱标签值时，我得到了以下错误。

  *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSMutableArray exchangeObjectAtIndex:withObjectAtIndex:]: index 16 beyond bounds [0 .. 3]'

我洗牌标签值数组的代码，

words = [[NSMutableArray alloc] initWithObjects:@"1", @"2", @"3",@"4", nil] ;

 NSUInteger count = [questar count];
for (NSUInteger i = 0; i < count; ++i) {
    // Select a random element between i and end of array to swap with.
    NSInteger nElements = count - i;
    NSInteger n = (arc4random() % nElements) + i;
    [words exchangeObjectAtIndex:i withObjectAtIndex:n];
}

我应该做些什么改变？有谁能帮我解决

Answer 1

您必须首先选择一个图像quester。您创建了索引n以从quester数组中获取对象吗？

words = [[NSMutableArray alloc] initWithObjects:@"1", @"2", @"3",@"4", nil] ;

NSUInteger count = [questar count];
for (NSUInteger i = 0; i < count; ++i) 
{
  // Select a random element between i and end of array to swap with.
  NSInteger nElements = count - i;
  NSInteger n = (arc4random() % nElements) + i;

  currentImage = [questar objectAtIndex:n];

  [words replaceObjectAtIndex:i withObject:currentImage];
}

或者，如果您想在数组中进行交换，请更改count为：

NSUInteger count = [words count];

Answer 2

以下：

NSInteger nElements = count - i;
NSInteger n = (arc4random() % nElements) + i;

应改为：

NSInteger nElements = count;
NSInteger n = (arc4random() % nElements);

Answer 3

[words exchangeObjectAtIndex:i withObjectAtIndex:n];

在上面的语句中，两者i的n值都应该小于words计数（这里是 4）。否则，你会得到例外。