objective-c - NSMutableArray : addObject "nil"?

Question

我在数组末尾添加“nil”时遇到问题，我得到“NSInvalidArgumentException”？

NSMutableArray *k = [NSMutableArray arrayWithCapacity:10];

for (int i=0; i<9; i++){
    [k addObject: @"blank"];
}
[k addObject: nil]; //<-- NSInvalidArgumentException

我需要在循环中逐项执行所有这些操作，然后添加“nil”。

谢谢

(然后我使用这个数组并初始化一个二维数组。问题是我无法用没有“nil”的数组成功“replaceObjectAtIndex”。如果我用“initWithObjects: @"blank", @"blank", @"blank", ... nil"构建“k”，这将起作用。然而，写 1000 个空白有点多。这就是循环的目的。)

//////这里是用于初始化和构建二维矩阵的试验和错误代码，用于从“CSV 文件”中读取和存储矩阵//////

///*
NSMutableArray *ppp = [NSMutableArray arrayWithCapacity:2];
NSMutableArray *kkk = [NSMutableArray arrayWithCapacity:20];

NSNull *myNull = [NSNull null];
for (int i=0; i<9; i++) {
    //[kkk addObject: [NSMutableString stringWithFormat: @"%d",i]];
    [kkk addObject: myNull];
}
//[kkk addObject: nil];

[ppp addObject:kkk];
[ppp addObject:kkk];
//*/


/*
// this is successful --> just uncomment this block and comment out the block above
[ppp addObject:[[NSMutableArray alloc] initWithObjects:
             @"z1",
             @"z2",
             @"z3",
             @"z4",
             @"z5",
             @"z6",
             @"z0gg",
             @"z0hh",
             @"z0ii",
             @"z0jj",
             nil
             ]];

[ppp addObject:[[NSMutableArray alloc] initWithObjects:
        @"a1",
        @"b2",
        @"c3",
        @"d4",
        @"e5",
        @"f6",
        nil
        ]];

*/

[[ppp objectAtIndex:0] replaceObjectAtIndex:1 withObject:@"HOTDOG"];
[[ppp objectAtIndex:1] replaceObjectAtIndex:1 withObject:@"HOHO"];
// HOHO will replace HOTDOG as well for the code not using "nil"

Answer 1

您不能将nil 添加到NSMutableArray，并且you will raise an exception if you try to .

虽然有 NSNull:

NSNull *myNull = [NSNull null];
[myMutableArray addObject:myNull];

但是，您可能会问自己为什么要尝试这样做。