Iphone 对NSArray（如MPMediaPickerController/iPod库）进行排序

我正在为iPhone开发一个自定义UIViewController，它模拟我的应用程序的本地文档目录中的文件的MPMediaPickerController的子集。特别是，我正在尝试重新创建“歌曲”选项卡。我已经成功地创建了我的新控制器，只是我不能像iPod库或MPMediaPickerController中那样对歌曲标题进行排序。以下是歌曲名称需要如何排序的示例：

真棒的歌名

酷歌

有史以来最黑暗的歌曲

我的歌名

一首很酷的歌

为什么是我

浪费4小时

---

如您所见，排序排除了歌曲标题中的前导文章，并将以数值开头的歌曲放在列表的末尾。有人能建议一个有效的排序功能，将这些tules考虑在内吗？

既然看起来没有人能提供解决方案，我想我会发布我提出的解决方案。首先，我为我的数据创建了一个模型：

@interface MyModel : NSObject
{
   NSString* _value;
   NSString* _sortableValue;
}

@property (nonatomic,copy) NSString* value;

- (NSString*)sortableValue;
- (NSString*)comparableString:(NSString*)str;

@end

模型的关键是comparableString方法，该方法用于创建sortableValue。以下是该模型的实现：

@implementation MyModel

@synthesize value=_value;

-(void)dealloc
{
   [_value release];
   [_sortableValue release];

   [super dealloc];
}

- (void)setValue:(NSString*)value
{
   [_value release];
   _value = [value copy];
   [_sortableValue release];
   _sortableTValue = nil;
}

- (NSString*)sortableValue
{
   if (_sortableValue == nil)
      _sortableValue = [[self comparableString:_value] retain];

   return _sortableValue;
}

- (NSString*)comparableString:(NSString*)str
{
   if (str == nil)
      return nil;
   else if ([str length] == 0)
      return [NSString stringWithString:str];

   NSCharacterSet* numbersSet = [NSCharacterSet decimalDigitCharacterSet];
   if ([str rangeOfCharacterFromSet:numbersSet options:0 range:NSMakeRange(0, 1)].location != NSNotFound)
      return [NSString stringWithString:str];

   NSRange range = NSMakeRange(0, [str length]);

   if ([str compare:@"a " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 2)] == NSOrderedSame)
      range.location = 2;
   else if ([str compare:@"an " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 3)] == NSOrderedSame)
      range.location = 3;
   else if ([str compare:@"the " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 4)] == NSOrderedSame)
      range.location = 4;

   range.length -= range.location;

   NSCharacterSet* lettersSet = [NSCharacterSet letterCharacterSet];
   NSUInteger letterOffset = [str rangeOfCharacterFromSet:lettersSet options:0 range:range].location;
   if (letterOffset == NSNotFound)
      return [NSString stringWithString:str];

   letterOffset -= range.location;
   range.location += letterOffset;
   range.length -= letterOffset;

   return [str substringWithRange:range];
}

@end

   // tableData will contain an NSArray for each populated section in the table view
   NSMutableDictionary* tableData = [NSMutableDictionary dictionary];

   NSMutableArray* myArray = [NSMutableArray array];
   // Populate myArray with instances of MyModel

   UILocalizedIndexedCollation* indexer = [UILocalizedIndexedCollation currentCollation];
   for (MyModel* data in myArray)
   {
      NSInteger index = [indexer sectionForObject:data collationStringSelector:@selector(sortableValue)];
      NSNumber* key = [[NSNumber alloc] initWithInteger:index];
      NSMutableArray* array = [tableData objectForKey:key];
      if (array == nil)
      {
         array = [NSMutableArray new]; // Will be released after creating a sorted array in the following section
         [tableData setObject:array forKey:key];
      }

      [array addObject:data];
      [key release];
   }

   [tableData enumerateKeysAndObjectsUsingBlock:^(id key, id array, BOOL* stop)
   {
      NSMutableArray* sortedArray = [[indexer sortedArrayFromArray:array collationStringSelector:@selector(sortableValue)] mutableCopy];
      [tableData setObject:sortedArray forKey:key];
      [array release];
   }];

除了从字符串中删除前导项目外，它还删除所有前导非字母字符。我的iPod库中有一首歌名为“$ell Your$oul”，它最终出现在MPMediaPickerController的E部分。我不确定如果我把最初的排序算法装箱，我会做什么，但我要与MPMediaPickerController保持一致，所以你就这样做了

拼图的最后一块是UILocalizedIndexedCollation类。这个方便的小助手类将帮助您对数据进行排序，使通过UITableViewDataSource向UITableView提供数据变得轻而易举。下面是一个关于如何将UILocalizedIndexedCollation类与模型结合使用的片段：

@implementation MyModel

@synthesize value=_value;

-(void)dealloc
{
   [_value release];
   [_sortableValue release];

   [super dealloc];
}

- (void)setValue:(NSString*)value
{
   [_value release];
   _value = [value copy];
   [_sortableValue release];
   _sortableTValue = nil;
}

- (NSString*)sortableValue
{
   if (_sortableValue == nil)
      _sortableValue = [[self comparableString:_value] retain];

   return _sortableValue;
}

- (NSString*)comparableString:(NSString*)str
{
   if (str == nil)
      return nil;
   else if ([str length] == 0)
      return [NSString stringWithString:str];

   NSCharacterSet* numbersSet = [NSCharacterSet decimalDigitCharacterSet];
   if ([str rangeOfCharacterFromSet:numbersSet options:0 range:NSMakeRange(0, 1)].location != NSNotFound)
      return [NSString stringWithString:str];

   NSRange range = NSMakeRange(0, [str length]);

   if ([str compare:@"a " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 2)] == NSOrderedSame)
      range.location = 2;
   else if ([str compare:@"an " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 3)] == NSOrderedSame)
      range.location = 3;
   else if ([str compare:@"the " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 4)] == NSOrderedSame)
      range.location = 4;

   range.length -= range.location;

   NSCharacterSet* lettersSet = [NSCharacterSet letterCharacterSet];
   NSUInteger letterOffset = [str rangeOfCharacterFromSet:lettersSet options:0 range:range].location;
   if (letterOffset == NSNotFound)
      return [NSString stringWithString:str];

   letterOffset -= range.location;
   range.location += letterOffset;
   range.length -= letterOffset;

   return [str substringWithRange:range];
}

@end

   // tableData will contain an NSArray for each populated section in the table view
   NSMutableDictionary* tableData = [NSMutableDictionary dictionary];

   NSMutableArray* myArray = [NSMutableArray array];
   // Populate myArray with instances of MyModel

   UILocalizedIndexedCollation* indexer = [UILocalizedIndexedCollation currentCollation];
   for (MyModel* data in myArray)
   {
      NSInteger index = [indexer sectionForObject:data collationStringSelector:@selector(sortableValue)];
      NSNumber* key = [[NSNumber alloc] initWithInteger:index];
      NSMutableArray* array = [tableData objectForKey:key];
      if (array == nil)
      {
         array = [NSMutableArray new]; // Will be released after creating a sorted array in the following section
         [tableData setObject:array forKey:key];
      }

      [array addObject:data];
      [key release];
   }

   [tableData enumerateKeysAndObjectsUsingBlock:^(id key, id array, BOOL* stop)
   {
      NSMutableArray* sortedArray = [[indexer sortedArrayFromArray:array collationStringSelector:@selector(sortableValue)] mutableCopy];
      [tableData setObject:sortedArray forKey:key];
      [array release];
   }];

关于UILocalizedIndexedCollation的一个简要说明（来自苹果的文档）：

如果应用程序提供 的Localizable.strings文件 当前的语言偏好 索引排序规则对象本地化 方法返回的每个字符串 由选择器标识

因此，请确保为要支持的每种语言提供一个Localizable.strings，否则您的表视图将只包含a-Z和#部分

---

我花了一段时间才弄清楚这方面的所有细节，所以我希望它对其他人有用。如果你看到我可以改进的方法，请告诉我

＞P>你可能需要考虑某些带有重音的字符，例如，艾，欧，，，，，， 因此，我稍微修改了您的代码以合并此。您的代码对我们所有iphone开发人员都是一个巨大的贡献

    - (NSString*)comparableString:(NSString*)str
{
    if (str == nil)
        return nil;
    else if ([str length] == 0)
        return [NSString stringWithString:str];

    NSCharacterSet* numbersSet = [NSCharacterSet decimalDigitCharacterSet];
    if ([str rangeOfCharacterFromSet:numbersSet options:0 range:NSMakeRange(0, 1)].location != NSNotFound)
        return [NSString stringWithString:str];

    NSRange range = NSMakeRange(0, [str length]);

    if ([str compare:@"a " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 2)] == NSOrderedSame)
        range.location = 2;
    else if ([str compare:@"an " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 3)] == NSOrderedSame)
        range.location = 3;
    else if ([str compare:@"the " options:(NSAnchoredSearch|NSCaseInsensitiveSearch) range:NSMakeRange(0, 4)] == NSOrderedSame)
        range.location = 4;

    range.length -= range.location;

    NSCharacterSet* lettersSet = [NSCharacterSet letterCharacterSet];
    NSUInteger letterOffset = [str rangeOfCharacterFromSet:lettersSet options:0 range:range].location;
    if (letterOffset == NSNotFound)
        return [NSString stringWithString:str];

    letterOffset -= range.location;
    range.location += letterOffset;
    range.length -= letterOffset;



//my modification starts here.........

    NSString * finalString = [str substringWithRange:range];
    NSString * firstCharString = [finalString substringToIndex:1];

    NSData * encodedData = [firstCharString dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
    NSString * encodedString = [[NSString alloc] initWithBytes:[encodedData bytes] length:[encodedData length] encoding:NSASCIIStringEncoding];
    if ([encodedString isEqualToString:@"?"]) {
        return finalString;
    }

    NSString * finalProcessedString = [finalString stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:encodedString];
    [encodedString release];
    return finalProcessedString;
}

---

+一个伟大的工人。我见过你的问题一次，但我没有时间找到解决办法。干得好，回答得真棒。您能否建议我如何使用

MPMediaQuery

实现此功能？我如何将其包括在

UITableViewController

类中，我是否需要为节创建一个单独的包含字母列表的数组？这由UILocalizedIndexedCollation在调用SortedArray FromArray:collationStringSelector:时自动处理，从我提供的最后一个代码片段开始。此外，您的添加只考虑第一个字符，如果字符串中的其他字符有重音符号，则会产生意外的结果。