A handy collection class for use with UITableView data sources, with filtering and indexing support baked in.

LRTableViewCollection.h

//
//  LRTableViewCollection.h
//  TellYouGov
//
//  Created by Luke Redpath on 19/04/2010.
//  Copyright 2010 LJR Software Limited. All rights reserved.
//

#import <UIKit/UIKit.h>


@interface LRTableViewCollection : NSObject {
  NSArray *objects;
  NSArray *indexedObjects;
  NSArray *filteredObjects;
  UILocalizedIndexedCollation *collation;
  SEL indexSelector;
  NSPredicate *filterPredicate;
}
@property (nonatomic, copy) NSArray *objects;
@property (nonatomic, retain) UILocalizedIndexedCollation *collation;
@property (nonatomic, assign) SEL indexSelector;
@property (nonatomic, retain) NSPredicate *filterPredicate;
@property (nonatomic, readonly) NSInteger sectionCount;

- (NSInteger)numberOfRowsInSection:(NSInteger)section;
- (id)objectAtIndexPath:(NSIndexPath *)indexPath;
- (void)appendObjects:(NSArray *)moreObjects;
@end

LRTableViewCollection.m

//
//  LRTableViewCollection.m
//  TellYouGov
//
//  Created by Luke Redpath on 19/04/2010.
//  Copyright 2010 LJR Software Limited. All rights reserved.
//

#import "LRTableViewCollection.h"
#import "NSArray+Indexing.h" 

// NSArray+Indexing can be found at http://gist.github.com/375409

@implementation LRTableViewCollection

@synthesize objects;
@synthesize collation;
@synthesize indexSelector;
@synthesize filterPredicate;
@dynamic sectionCount;

- (void)dealloc {
  [objects release];
  [indexedObjects release];
  [filteredObjects release];
  [collation release];
  [filterPredicate release];
  [super dealloc];
}

- (id)init;
{
  if (self = [super init]) {
    objects = [[NSArray alloc] init];
  }
  return self;
}

- (void)setObjects:(NSArray *)array;
{
  [objects release]; objects = [array copy];

  if (self.collation) {
    indexedObjects = [[objects indexUsingCollation:self.collation withSelector:indexSelector] retain];
  }
}

- (void)appendObjects:(NSArray *)moreObjects;
{
  self.objects = [objects arrayByAddingObjectsFromArray:moreObjects];
}

- (void)setFilterPredicate:(NSPredicate *)predicate;
{
  if (predicate != filterPredicate) {
    [filterPredicate release]; filterPredicate = [predicate retain];
    
    if (filterPredicate == nil) {
      [filteredObjects release]; filteredObjects = nil;
    } else {
      filteredObjects = [[self.objects filteredArrayUsingPredicate:self.filterPredicate] retain];
    }    
  }
}

#pragma mark -
#pragma mark Dynamic collection properties

- (NSInteger)sectionCount;
{
  if (self.filterPredicate == nil && indexedObjects != nil) {
    return [indexedObjects count];
  }
  return 1;
}

- (NSInteger)numberOfRowsInSection:(NSInteger)section;
{
  if (self.filterPredicate) {
    return [filteredObjects count];
  } else if (indexedObjects != nil) {
    return [[indexedObjects objectAtIndex:section] count];
  }
  return [objects count];
}

- (id)objectAtIndexPath:(NSIndexPath *)indexPath;
{
  if (self.filterPredicate) {
    return [filteredObjects objectAtIndex:indexPath.row];
  } else if (indexedObjects != nil) {
    return [[indexedObjects objectAtIndex:indexPath.section] objectAtIndex:indexPath.row];
  }
  return [objects objectAtIndex:indexPath.row];
}

@end