拋去陣列捕獲的異常

Question

林。

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

我洗牌標籤值的陣列碼，

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]; 
} 

，我應該做出什麼樣的變化？任何一個可以幫助我解決

Answer 1

[words exchangeObjectAtIndex:i withObjectAtIndex:n]; 

在上面的語句，既i和n應該有一個值比words數少（這裏是4）。否則，你會得到例外。

Answer 2

你必須首先從quester選擇圖像。你創建索引n從quester數組中取對象沒有？

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，如果你想爲陣列變化count內交換：

NSUInteger count = [words count]; 

Answer 3

以下：

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

應改爲：

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