Building Sections
When working with groups and sections, think two dimensionally. Section arrays let you store and access the members of data in a section-by-section structure. Implement this approach by creating an array of arrays. A section array can store one array for each section, which in turn contains the titles for each cell.
Predicates help you build sections from a list of strings. The following method alphabetically retrieves items from a flat array. The beginswith predicate matches each string that starts with the given letter:
- (NSArray *)itemsInSection:(NSInteger)section { NSPredicate *predicate = [NSPredicate predicateWithFormat: @"SELF beginswith[cd] %@", [self firstLetter:section]]; ...
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