ios - nsmutablearray.count和tableview indexpath.row之间的比较给出了奇怪的结果

Question

我有下面。

NSLog(@"aaaa===%ld==%ld", indexPath.row, (rowsOptionss.count-1));

if (indexPath.row>(rowsOptionss.count-1)) {
    NSLog(@"000===this is true");
} else {
    NSLog(@"000===this is false");
}

if (0>-1) {
    NSLog(@"001===this is true");
} else {
    NSLog(@"001===this is false");
}

这给了我如下结果。

2016-02-04 13:02:15.316 ClubsFans[7085:16944474] aaaa===0==-1
2016-02-04 13:02:15.316 ClubsFans[7085:16944474] 000===this is false
2016-02-04 13:02:15.316 ClubsFans[7085:16944474] 001===this is true

我应该说

2016-02-04 13:02:15.316 ClubsFans[7085:16944474] aaaa===0==-1
2016-02-04 13:02:15.316 ClubsFans[7085:16944474] 000===this is true >> this should be true
2016-02-04 13:02:15.316 ClubsFans[7085:16944474] 001===this is true

知道为什么会出错吗？

Answer 1

这可以帮助您了解:

NSIndexPath* indexPath = nil;
NSArray * rowsOptionss = [NSArray array];
NSLog(@"aaaa===%ld==%ld", indexPath.row, (rowsOptionss.count-1));
NSLog(@"real value: bbbb===%ld==%u", (long)indexPath.row, (rowsOptionss.count-1));

if (indexPath.row>(rowsOptionss.count-1)) {
    NSLog(@"000===this is true");
} else {
    NSLog(@"000===this is false");
}

if (0>-1) {
    NSLog(@"001===this is true");
} else {
    NSLog(@"001===this is false");
}

rowsOptionss.count是无符号的 (NSUInteger)，如果执行 -1操作，您将获得非常大的正数，该数字始终大于0。

那是日志:

 aaaa===0==-1
 real value: bbbb===0==4294967295
 000===this is false
 001===this is true

如果您需要带符号的int，请改用以下方法:

NSInteger tempInt = rowsOptionss.count;
tempInt --;
LOG(@"tempInt %i", tempInt);