didReorderHandler
The handler that processes a reordering transaction.
Declaration
@property (nonatomic, copy) void (^didReorderHandler)(NSDiffableDataSourceTransaction<id,id> *);Discussion
The system calls the didReorderHandler handler after a reordering transaction (NSDiffableDataSourceTransaction) occurs, so you can update your data backing store with information about the changes.
// Allow every item to be reordered
dataSource.reorderingHandlers.canReorderItem = { item in return true }
// Option 1: Update the backing store from a CollectionDifference
dataSource.reorderingHandlers.didReorder = { [weak self] transaction in
guard let self = self else { return }
if let updatedBackingStore = self.backingStore.applying(transaction.difference) {
self.backingStore = updatedBackingStore
}
}
// Option 2: Update the backing store from the final item identifiers
dataSource.reorderingHandlers.didReorder = { [weak self] transaction in
guard let self = self else { return }
self.backingStore = transaction.finalSnapshot.itemIdentifiers
}