Отзывчивый searchbar

swift_searchbar.swift

func searchBar(searchBar: UISearchBar, textDidChange searchText: String) {
    weak var weakSelf: ProductPickerTableViewController = self
    var searchDelay: Double = 0.3
    if self.searchBlock != nil {
        //We cancel the currently scheduled block
        cancel_block(self.searchBlock)
    }
    self.searchBlock = dispatch_after_delay(searchDelay, {() -> Void in
        //We "enqueue" this block with a certain delay. It will be canceled if the user types faster than the delay, otherwise it will be executed after the specified delay
        weakSelf.currentSearchOperation.cancel()
        weakSelf.currentSearchOperation = NSBlockOperation.blockOperationWithBlock({() -> Void in
            if searchText.length() {
                weakSelf.searchProducts = weakSelf.food.productsBySearchPhrase(searchText)
                weakSelf.isSearchNowProducts = true
            }
            else {
                weakSelf.isSearchNowProducts = false
            }
            dispatch_async(dispatch_get_main_queue(), {() -> Void in
                weakSelf.tableView.reloadData()
                weakSelf.currentSearchOperation = nil
            })
        })
        let label: Character = "ru.rinatabidullin.unique.search"
        var queue: dispatch_queue_t = dispatch_queue_create(label, DISPATCH_QUEUE_SERIAL)
        dispatch_async(queue, {() -> Void in
            weakSelf.currentSearchOperation.start()
        })
    })
}