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

Question

UILocalizedIndexedCollation工作怎么样？

我正在从文档中读取simpleIndexedTableView 示例代码,RootViewController初始化,我们发送一些数据(rootViewController.timeZonesArray = timeZones;)但此时,collation已经在视图控制器中使用:

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

基本上这就是魔术似乎发生的地方,那么 [collation sectionTitles]包含什么呢？一些必须是自动的,但我不知道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

[collation sectionTitles]只需包含标准字母排序,以便在tableview的右侧显示.即使您只有以"B"和"F"开头的项目,侧面的索引也始终显示完整的字母.但由于用于排序字符串的标准字母表根据区域设置而变化,因此Apple让我们UILocalizedIndexedCollation可以轻松向用户显示他们期望的内容.