UITableView's reusableTableCells

@implementation UITableView (T)

• (NSMutableArray *)reusableCells
  {
  return [self performSelector:@selector(_reusableTableCells)];
  }

@end

@interface ViewController ()

@property (nonatomic, strong) UITableView *tableView;

@end

@implementation ViewController

• (void)viewDidLoad
  {
  [super viewDidLoad];

  self.tableView = [[UITableView alloc] initWithFrame:self.view.bounds];
  self.tableView.delegate = self;
  self.tableView.dataSource = self;

  [self.view addSubview:self.tableView];

  [self reloadData];

  [self performSelector:@selector(reloadData) withObject:nil afterDelay:.8];
  }

• (void)reloadData
  {
  NSLog(@"--------------------");
  NSLog(@"before reloadData");
  NSLog(@"%@", [self.tableView valueForKey:@"_reusableTableCells"]);

  [self.tableView reloadData];

  NSLog(@"after reloadData");
  NSLog(@"%@", [self.tableView valueForKey:@"_reusableTableCells"]);
  }

• (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
  {
  return 1;
  }

• (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
  {
  return 3;
  }

• (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
  {
  UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"test"];
  if (!cell) {
  cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"test"];
  }
  NSLog(@"make cell row:%d", indexPath.row);

  return cell;
  }
  @end

2014-10-17 19:23:09.334 test[52333:4372534] --------------------
2014-10-17 19:23:09.335 test[52333:4372534] before reloadData
2014-10-17 19:23:09.335 test[52333:4372534] (null)
2014-10-17 19:23:09.335 test[52333:4372534] after reloadData
2014-10-17 19:23:09.335 test[52333:4372534] {
}
2014-10-17 19:23:09.344 test[52333:4372534] make cell row:0
2014-10-17 19:23:09.347 test[52333:4372534] make cell row:1
2014-10-17 19:23:09.347 test[52333:4372534] make cell row:2
2014-10-17 19:23:10.136 test[52333:4372534] --------------------
2014-10-17 19:23:10.136 test[52333:4372534] before reloadData
2014-10-17 19:23:10.137 test[52333:4372534] {
}
2014-10-17 19:23:10.137 test[52333:4372534] after reloadData
2014-10-17 19:23:10.137 test[52333:4372534] {

    test =     (
        "

    其中test为NSMutableDictionary的key.
     (
        "

}
2014-10-17 19:23:10.137 test[52333:4372534] make cell row:0
2014-10-17 19:23:10.138 test[52333:4372534] make cell row:1
2014-10-17 19:23:10.138 test[52333:4372534] make cell row:2

参考：
https://gist.github.com/hirohisa/36b61d628a3a1e6866fe
https://github.com/Microsoft/WinObjC/blob/master/Frameworks/UIKit/UITableView.mm