Question

我有一个带有单元格的TableView，我向它们添加了一个Observer。我在willDisplay上添加了一个Observer给Cell：

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    let cell = cell as! CustomCell
    cell.watchFrameChanges()
}

我在didEndDisplaying上删除它：

func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath) {
    let cell = cell as! CustomCell
    cell.unwatchFrameChanges()
}

CustomCell方法：

func watchFrameChanges() -> Void {
    self.addObserver(self, forKeyPath: "frame", options: NSKeyValueObservingOptions.new, context: nil)
}

func unwatchFrameChanges() -> Void {
    if self.observationInfo != nil {
        self.removeObserver(self, forKeyPath: "frame")
    }
}

问题是，当我从包含此TableView的ViewController导航回来时，Observers不会被删除，我收到此错误：

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'An instance 0x7f892d216800 of class MyProject.CustomCell was deallocated while key value observers were still registered with it.

如何在导航时正确删除观察者？

Answer 1

试试这个

override func viewWillDisappear(animated: Bool) {    
    super.viewWillDisappear(animated)
    for row in 0...(array.count-1) {
        let indexPath = NSIndexPath(forRow: row, inSection: 0)
        if let cell = tableView.cellForRowAtIndexPath(indexPath) as? CustomCell {
            cell.unwatchFrameChanges()
        }
    }
}

在后退导航中从单元格中删除观察者

1 个答案: