'NSArray'没有可见的@interface声明选择器'exchangeObjectAtIndex:withObjectAtIndex

Question

我试图改组一个数组,但我得到一个"没有可见的@interface for'NSArray'在最后一个语句中声明选择器'exchangeObjectAtIndex:withObjectAtIndex:'.

如何宣布bArray？

NSArray *bArray;

并在

 - (void)viewDidLoad
      [self shuffleb];

然后

-(void) shufflb
   {
 bArray = [NSArray arrayWithObjects:
             @"ca",
             @"do",
             @"ba",
             @"tr",
             @"bu",
             @"bl",
             @"bo",
             @"pu",
             nil];

NSInteger count = [bArray 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;
    n = (arc4random() % nElements) + i;
    [bArray exchangeObjectAtIndex:i withObjectAtIndex:n];
}

Answer 1

exchangeObjectAtIndex 是NSMutableArray的方法.

https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSMutableArray_Class/Reference/Reference.html