检测UITableViewCell何时超出范围

func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    let cellRect = tableView.rectForRow(at: indexPath)
    let visibleRect = tableView.bounds
    if !visibleRect.intersects(cellRect) {
        // 当前cell已经超出范围
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    tableView.addObserver(self, forKeyPath: "contentOffset", options: .new, context: nil)
}

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if keyPath == "contentOffset" {
        let visibleCells = tableView.visibleCells
        for cell in visibleCells {
            let cellRect = cell.frame
            let visibleRect = tableView.bounds
            if !visibleRect.intersects(cellRect) {
                // 当前cell已经超出范围
            }
        }
    }
}

deinit {
    tableView.removeObserver(self, forKeyPath: "contentOffset")
}

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let visibleRect = tableView.bounds
    let visibleCells = tableView.visibleCells
    for cell in visibleCells {
        let cellRect = cell.frame
        if !visibleRect.intersects(cellRect) {
            // 当前cell已经超出范围
        }
    }
}