抛去阵列捕获的异常

Question

林。

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

我洗牌标签值的阵列码，

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]; 
} 

，我应该做出什么样的变化？任何一个可以帮助我解决

Answer 1

[words exchangeObjectAtIndex:i withObjectAtIndex:n]; 

在上面的语句，既i和n应该有一个值比words数少（这里是4）。否则，你会得到例外。

Answer 2

你必须首先从quester选择图像。你创建索引n从quester数组中取对象没有？

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，如果你想为阵列变化count内交换：

NSUInteger count = [words count]; 

Answer 3

以下：

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

应改为：

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