NSMutableArray没有被保存

Question

我正在尝试将对象(NSNumbers)插入到NSMutable数组中,但是当我检查它时,objectAtElement总是返回0.

NSNumber *indexNum = [NSNumber numberWithInt:indexInt];
[last100 insertObject:indexNum atIndex:prevCount];
NSLog(@"Entry #%d : %d", prevCount, (int)[last100 objectAtIndex:prevCount]);
prevCount++;

indexInt通过这种方法进入,我已经检查过它的有效性.indexNum也经过检查和比赛indexInt.问题NSLog(@"Entry #%d : %d", prevCount, (int)[last100 objectAtIndex:prevCount]);始终是回归

2012-01-08 14:08:11.551 ThoughtSpreader[20746:fb03] Entry #9 : 0 条目号将改变,但0始终存在.

哦,我每次插入新内容后都检查了[last100 count],它总是返回0,所以我相信它是如何插入NSMutable数组的问题

Answer 1

如果你的计数总是返回0,你可能没有实际实例化你的计数NSMutableArray.

NSMutableArray *array = [NSMutableArray array];

[array addObject:[NSNumber numberWithInt:1]];

NSLog(@"%lu", [array count]); // Count => 1

//-------

array = nil;

[array addObject:[NSNumber numberWithInt:1]]; // Calling methods on nil is a no-op

NSLog(@"%lu", [array count]); // Count => 0

更新%d以%lu感谢@markhunte - 如果不对其进行测试,很难记住更精细的细节