iOS:编辑 TableView 中的项目问题

Question

所以我尝试为 TableView 中的行编写删除编辑行为。但是，当我在选择一行后按下删除键时，该行不会从 tableView 中删除。当我第二次尝试执行此操作时，收到一条错误消息，指出发现了意外的 nil 值。

override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == .Delete {   // Handle the Delete action
        // Obtain the name of the genre of movie to be deleted
        let genre: String = genres[indexPath.section]

        // Obtain the list of movies in the genre as AnyObject
        let movies: AnyObject? = applicationDelegate.dict_Genres_dict2[genre]
        let movArray: [String] = movies?.allKeys as! [String] //The nil value is unwrapped on this line
        // Typecast the AnyObject to Swift array of String objects
        var moviesOfGenre: Array<String> = movArray 

        // Delete the identified movie at row
        moviesOfGenre.removeAtIndex(indexPath.row)

        if moviesOfGenre.count == 0 {
            // If no movie remains in the array after deletion, then we need to also delete the genre
            applicationDelegate.dict_Genres_dict2.removeObjectForKey(genre)

            // Since the dictionary has been changed, obtain the genre names again
            genres = applicationDelegate.dict_Genres_dict2.allKeys as! [String]

            // Sort the genre names within itself in alphabetical order
            genres.sortInPlace { $0 < $1 }
        }
        else {
            // At least one more movie remains in the array; therefore, the genre stays.

            // Update the new list of movie for the genre in the NSMutableDictionary
            applicationDelegate.dict_Genres_dict2.setValue(moviesOfGenre, forKey: genre)
        }

        // Reload the rows and sections of the Table View 
        tableView.reloadData()
    }
}

我已经标记了哪一行接收到 nil 值。任何朝着正确方向的插入都会是最有帮助的。谢谢!

Answer 1

删除数组项后。您也需要从表中删除该项目。当您尝试再次删除数组项目时，它显示 nil，因为该项目不可用，但表没有从 View 中删除该项目。所以您需要删除它也从表中...

        genres.removeAtIndex(indexPath.row) // or section , delete according to your app   
        tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Automatic)

为什么要删除要删除的项目的一部分。您没有从表中删除流派项目。您只删除了 movieOfGenre。您还需要删除 TableView 项目(流派)。也从表中删除流派。

您还可以使用滑动删除功能:-

func tableView(tableView: UITableView!, canEditRowAtIndexPath indexPath: NSIndexPath!) -> Bool {
    return true
}

func tableView(tableView: UITableView!, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath!) {
    if (editingStyle == .Delete) {
   // handle delete (by removing the data from your array and updating the tableview)

    self.tableView.beginUpdates()
    self.genres.removeObjectAtIndex(indexPath.row) // also remove an array object if exists.
    self.tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Left)
    self.tableView.endUpdates()
}