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目标C:比较两个不正常工作的字符串

objective-c

Oh Danny Boy · 技术社区 · 14 年前

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {

    id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];

    if(tempArray != nil){
        for (int i = 0; i < [tempArray count]; i++)
        {
            if([[sectionInfo indexTitle] isEqualToString:[tempArray objectAtIndex:i]])
        //  if([sectionInfo indexTitle] == [tempArray objectAtIndex:i])
            {
                NSLog(@"found");
                break;
            } else
                {
                    NSLog(@"Not found %@", [sectionInfo indexTitle]);
                    [tempArray addObject:[sectionInfo indexTitle]];
                    NSLog(@"array %@", tempArray);
                    return [tempArray objectAtIndex:i];
                }
        }
    } 
}

if语句中字符串的比较永远不会解析为true。为了测试目的,示例数据有两个重复的实例。注释行是一个替代行,尽管我认为不正确,但尝试将节与temparray中的字符串进行比较。

我做错什么了?

而且,所有数据都是大写字母,所以比较不是大小写的问题。

编辑:

NSLogs:

                NSLog(@"Not found %@", [sectionInfo indexTitle]);
                NSLog(@"section: %d", section);
                NSLog(@"[sectionInfo indexTitle] %@", [sectionInfo indexTitle]);
                NSLog(@"[sectionInfo objects] %@", [[sectionInfo objects] valueForKey:@"name"]);
                NSLog(@"array %@", tempArray);

给我这些结果:

2010-06-08 11:25:03.276 XYZApplication[5287:207] Not found Z
2010-06-08 11:25:03.277 XYZApplication[5287:207] section: 10
2010-06-08 11:25:03.279 XYZApplication[5287:207] [sectionInfo indexTitle] Z
2010-06-08 11:25:03.284 XYZApplication[5287:207] [sectionInfo objects] (
    Z
)
2010-06-08 11:25:03.284 XYZApplication[5287:207] array (
    ""
)
2010-06-08 11:25:03.285 XYZApplication[5287:207] Not found A
2010-06-08 11:25:03.285 XYZApplication[5287:207] section: 0
2010-06-08 11:25:03.286 XYZApplication[5287:207] [sectionInfo indexTitle] A
2010-06-08 11:25:03.286 XYZApplication[5287:207] [sectionInfo objects] (
    "Andy the Clown"
)
2010-06-08 11:25:03.287 XYZApplication[5287:207] array (
    "",
    Z
)
2010-06-08 11:25:03.288 XYZApplication[5287:207] Not found B
2010-06-08 11:25:03.289 XYZApplication[5287:207] section: 1
2010-06-08 11:25:03.289 XYZApplication[5287:207] [sectionInfo indexTitle] B
2010-06-08 11:25:03.290 XYZApplication[5287:207] [sectionInfo objects] (
    "Baseball Annie"
)
2010-06-08 11:25:03.291 XYZApplication[5287:207] array (
    "",
    Z,
    A
)
2010-06-08 11:25:03.291 XYZApplication[5287:207] Not found B
2010-06-08 11:25:03.292 XYZApplication[5287:207] section: 2
2010-06-08 11:25:03.292 XYZApplication[5287:207] [sectionInfo indexTitle] B
2010-06-08 11:25:03.293 XYZApplication[5287:207] [sectionInfo objects] (
    "Baseball Bugs"
)
2010-06-08 11:25:03.293 XYZApplication[5287:207] array (
    "",
    Z,
    A,
    B
)
2010-06-08 11:25:03.294 XYZApplication[5287:207] Not found D
2010-06-08 11:25:03.295 XYZApplication[5287:207] section: 3
2010-06-08 11:25:03.295 XYZApplication[5287:207] [sectionInfo indexTitle] D
2010-06-08 11:25:03.296 XYZApplication[5287:207] [sectionInfo objects] (
    ""
)
2010-06-08 11:25:03.296 XYZApplication[5287:207] array (
    "",
    Z,
    A,
    B,
    B
)
2010-06-08 11:25:03.296 XYZApplication[5287:207] Not found E
2010-06-08 11:25:03.304 XYZApplication[5287:207] section: 4
2010-06-08 11:25:03.305 XYZApplication[5287:207] [sectionInfo indexTitle] E
2010-06-08 11:25:03.306 XYZApplication[5287:207] [sectionInfo objects] (
    E
)
2010-06-08 11:25:03.306 XYZApplication[5287:207] array (
    "",
    Z,
    A,
    B,
    B,
    D
)
2010-06-08 11:25:03.307 XYZApplication[5287:207] Not found F
2010-06-08 11:25:03.307 XYZApplication[5287:207] section: 5
2010-06-08 11:25:03.308 XYZApplication[5287:207] [sectionInfo indexTitle] F
2010-06-08 11:25:03.310 XYZApplication[5287:207] [sectionInfo objects] (
    Frank
)
2010-06-08 11:25:03.310 XYZApplication[5287:207] array (
    "",
    Z,
    A,
    B,
    B,
    D,
    E
)
2010-06-08 11:25:03.311 XYZApplication[5287:207] Not found H
2010-06-08 11:25:03.311 XYZApplication[5287:207] section: 6
2010-06-08 11:25:03.312 XYZApplication[5287:207] [sectionInfo indexTitle] H
2010-06-08 11:25:03.313 XYZApplication[5287:207] [sectionInfo objects] (
    H
)
2010-06-08 11:25:03.313 XYZApplication[5287:207] array (
    "",
    Z,
    A,
    B,
    B,
    D,
    E,
    F
)
2010-06-08 11:25:03.314 XYZApplication[5287:207] Not found J
2010-06-08 11:25:03.315 XYZApplication[5287:207] section: 7
2010-06-08 11:25:03.315 XYZApplication[5287:207] [sectionInfo indexTitle] J
2010-06-08 11:25:03.316 XYZApplication[5287:207] [sectionInfo objects] (
    J
)
2010-06-08 11:25:03.316 XYZApplication[5287:207] array (
    "",
    Z,
    A,
    B,
    B,
    D,
    E,
    F,
    H
)
2010-06-08 11:25:03.317 XYZApplication[5287:207] Not found J
2010-06-08 11:25:03.317 XYZApplication[5287:207] section: 8
2010-06-08 11:25:03.329 XYZApplication[5287:207] [sectionInfo indexTitle] J
2010-06-08 11:25:03.330 XYZApplication[5287:207] [sectionInfo objects] (
    Joe
)
2010-06-08 11:25:03.330 XYZApplication[5287:207] array (
    "",
    Z,
    A,
    B,
    B,
    D,
    E,
    F,
    H,
    J
)
2010-06-08 11:25:03.335 XYZApplication[5287:207] Not found L
2010-06-08 11:25:03.336 XYZApplication[5287:207] section: 9
2010-06-08 11:25:03.336 XYZApplication[5287:207] [sectionInfo indexTitle] L
2010-06-08 11:25:03.337 XYZApplication[5287:207] [sectionInfo objects] (
    L
)
2010-06-08 11:25:03.337 XYZApplication[5287:207] array (
    "",
    Z,
    A,
    B,
    B,
    D,
    E,
    F,
    H,
    J,
    J
)

3 回复 | 直到 12 年前

JeremyP 14 年前

temparray的第一个元素似乎总是空字符串。在日志中,[sectioninfo indextitle]绝不是空字符串。

因为你第一次找不到东西就退出了这个方法,你永远不会得到一个真正的比较。

另外,我注意到您在每次未找到的迭代中,都会将未找到的[sectioninfo indextitle]添加到您的temparray中。这就是你真正想要的吗?

而且,如果你找到了一个匹配的,你不会返回任何东西。你应该得到一个编译器警告,说这个方法并不总是返回一个值。

我有点猜测,但我认为你想要:

    for (int i = 0; i < [tempArray count]; i++) // NB [nil count] returns 0 so your test for a nil tempArray is unnecessary
    {
        if([[sectionInfo indexTitle] isEqualToString:[tempArray objectAtIndex:i]])
        {
            NSLog(@"found");
            return [tempArray objectAtIndex:i];
        } 
        else
        {
            NSLog(@"Not found %@", [sectionInfo indexTitle]);
            NSLog(@"array %@", tempArray);
        }
    }
    [tempArray addObject:[sectionInfo indexTitle]];
    return ???? // I don't know what you want returned in this case:

编辑评论如下:

我想我终于明白你想做什么了:

如果你已经有了一个和你现在要交付的相同的部分标题,你想返回nil,这样该部分就没有标题了。在这种情况下,代码应该如下所示:

    for (int i = 0; i < [tempArray count]; i++) // NB [nil count] returns 0 so your test for a nil tempArray is unnecessary
    {
        if([[sectionInfo indexTitle] isEqualToString:[tempArray objectAtIndex:i]])
        {
            NSLog(@"found");
            return nil;
        } 
        else
        {
            NSLog(@"Not found %@", [sectionInfo indexTitle]);
            NSLog(@"array %@", tempArray);
        }
    }
    [tempArray addObject:[sectionInfo indexTitle]];
    return [sectionInfo indexTitle];

但是

您可以使用nsmutableset代替:

if ([tempSet containsObject: [sectionInfo indexTitle]])
{
    return nil;
}
else
{
    [tempSet addObject: [sectionInfo indexTitle]];
    return [sectionInfo indexTitle];
}

Chris Johnsen 14 年前

当第一个元素不匹配时, return 在else分支中,将中止搜索。如果第一个元素是匹配的,那么__然后__分支将跳出循环(我猜还有更多的代码来为这种情况提供返回值?).

也许 返回 应该替换 break 在_然后_稹分支中?

另外,因为您已经有了所需的字符串 [sectionInfo indexTitle] ,为什么要手动搜索?你只需要检查它是否在列表中吗?可能是这样的,而不是循环:

if ([tempArray containsObject: [sectionInfo indexTitle]]) {
    return [sectionInfo indexTitle];
} else {
    return @"<invalid>"; // or whatever
}

James 14 年前

你确定里面的东西 tempArray 真的 NSString ? isEqualToString 如果它们是其他类型,则返回false。

另外,字符串中可以有尾随空格吗?