iphone - UILocalizedIndexedCollat​​ion 是如何工作的？ (文档中的示例代码)

Question

UILocalizedIndexedCollat​​ion 是如何工作的？

我正在阅读 simpleIndexedTableView sample code根据文档，RootViewController 已初始化，我们向其发送一些数据(rootViewController.timeZonesArray = timeZones;)，但此时，collat​​ion 是已在 View Controller 中使用:

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // The number of sections is the same as the number of titles in the collation.
    return [[collation sectionTitles] count];
}

基本上这就是魔法似乎发生的地方，那么 [collat​​ion sectionTitles] 包含什么？某些东西必须是自动的，但我不明白整个事情是如何运作的？

- (void)configureSections {

    // Get the current collation and keep a reference to it.
    self.collation = [UILocalizedIndexedCollation currentCollation];

    NSInteger index, sectionTitlesCount = [[collation sectionTitles] count];

    NSMutableArray *newSectionsArray = [[NSMutableArray alloc] initWithCapacity:sectionTitlesCount];

    // Set up the sections array: elements are mutable arrays that will contain the time zones for that section.
    for (index = 0; index < sectionTitlesCount; index++) {
        NSMutableArray *array = [[NSMutableArray alloc] init];
        [newSectionsArray addObject:array];
        [array release];
    }

    // Segregate the time zones into the appropriate arrays.
    for (TimeZoneWrapper *timeZone in timeZonesArray) {

        // Ask the collation which section number the time zone belongs in, based on its locale name.
        NSInteger sectionNumber = [collation sectionForObject:timeZone collationStringSelector:@selector(localeName)];

        // Get the array for the section.
        NSMutableArray *sectionTimeZones = [newSectionsArray objectAtIndex:sectionNumber];

        //  Add the time zone to the section.
        [sectionTimeZones addObject:timeZone];
    }

    // Now that all the data's in place, each section array needs to be sorted.
    for (index = 0; index < sectionTitlesCount; index++) {

        NSMutableArray *timeZonesArrayForSection = [newSectionsArray objectAtIndex:index];

        // If the table view or its contents were editable, you would make a mutable copy here.
        NSArray *sortedTimeZonesArrayForSection = [collation sortedArrayFromArray:timeZonesArrayForSection collationStringSelector:@selector(localeName)];

        // Replace the existing array with the sorted array.
        [newSectionsArray replaceObjectAtIndex:index withObject:sortedTimeZonesArrayForSection];
    }

    self.sectionsArray = newSectionsArray;
    [newSectionsArray release]; 
}

谢谢你的帮助

Answer 1

[collat​​ion sectionTitles] 仅包含标准字母表排序，以便沿 tableview 的右侧显示。即使您只有以“B”和“F”开头的项目，侧面的索引也会始终显示完整的字母表。但由于用于对字符串进行排序的标准字母表会根据区域设置而变化，Apple 为我们提供了 UILocalizedIndexedCollat​​ion 以便轻松向用户展示他们的期望。