You can accomplish:

Inserting,Deleting,and Moving Sections and Items To insert,delete,
or move a single section or item,follow these steps:

1. Update the data in your data source object.
2. Call the appropriate method of the collection view to insert or delete the section or item.

It is critical that you update your data source before notifying the
collection view of any changes. The collection view methods assume
that your data source contains the currently correct data. If it does
not,the collection view might receive the wrong set of items from
your data source or ask for items that are not there and crash your
app. When you add,or move a single item programmatically,the
collection view’s methods automatically create animations to reflect
the changes. If you want to animate multiple changes together,though,
you must perform all insert,or move calls inside a block and
pass that block to the performBatchUpdates:completion: method. The
batch update process then animates all of your changes at the same
time and you can freely mix calls to insert,or move items
within the same block.

从你的问题：你可以例如注册一个手势识别器,并插入一个新的单元格
做如下：

在

// in .h 
@property (nonatomic,strong) NSMutableArray *data;

// in .m 
@synthesize data
// 

- (void)ViewDidLoad{
      //.... 

    myCollectonView.dataSource = self;
    myCollectionView.delegate = self; 
    data = [[NSMutableArray alloc] initWithObjects:@"0",@"1",@"2" @"3",@"4",@"5",@"6",@"7",@"8",@"9",@"10",@"11",@"12",@"13",@"14",@"15",nil];

    UISwipeGestureRecognizer *swipeDown = 
     [[UISwipeGestureRecognizer alloc] 
       initWithTarget:self action:@selector(addNewCell:)];
    swipeDown.direction = UISwipeGestureRecognizerDirectionDown;
        [self.view addGestureRecognizer:swipeDown];
    //.. 
} 


-(void)addNewCell:(UISwipeGestureRecognizer *)downGesture {
    NSArray *newData = [[NSArray alloc] initWithObjects:@"otherData",nil];
    [self.myCollectionView performBatchUpdates:^{
        int resultsSize = [self.data count]; //data is the prevIoUs array of data
        [self.data addObjectsFromArray:newData];
        NSMutableArray *arrayWithIndexPaths = [NSMutableArray array];

        for (int i = resultsSize; i < resultsSize + newData.count; i++) {
            [arrayWithIndexPaths addObject:[NSIndexPath indexPathForRow:i 
                                                              inSection:0]];
        }
        [self.myCollectionView insertItemsAtIndexPaths:arrayWithIndexPaths];
    } completion:nil];

}