在Swift / iOS中从UITableView删除行并从NSUserDefaults更新数组的正确方法

问题描述：

从 UITableView 删除行并从NSUserDefaults更新数组的正确方法是什么？

What is the proper way to delete rows from UITableView and update array from NSUserDefaults?

例如，我从 NSUserDefaults 中读取一个数组，并将其内容提供给 UITableView ，我还允许用户删除 UITableView 中的项目我不确定是何时读写 NSUserDefaults 以便表更新一旦删除行。如您所见，我首先在 viewDidLoad 方法中读取数组，然后在 commitEditingStyle 方法中重新保存它。使用这种方法，删除行后，我的表不会重新加载。

In the following example I'm reading an array from NSUserDefaultsand feeding a UITableView with its content, I'm also allowing the user to delete items in the UITableView what I'm not sure is when to read and write to NSUserDefaults so the table updates as soon as a row is deleted. As you can see I start by reading the array the in the viewDidLoad method and re-saving it in the commitEditingStyle method. With this method my table is not reloading when a row is deleted.

override func viewDidLoad() {
    super.viewDidLoad()
     // Lets assume that an array already exists in NSUserdefaults.
     // Reading and filling array with content from NSUserDefaults.
    let userDefaults = NSUserDefaults.standardUserDefaults()
    var array:Array = userDefaults.objectForKey("myArrayKey") as? [String] ?? [String]()
}

func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return array.count
}

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = UITableViewCell()
    cell.textLabel!.text = array[indexPath.row]
    return cell
}

func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == UITableViewCellEditingStyle.Delete {
        array.removeAtIndex(indexPath.row)
        tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Automatic)
    }
  // Save array to update NSUserDefaults     
 let userDefaults = NSUserDefaults.standardUserDefaults()
 userDefaults.setObject(array, forKey: "myArrayKey")


 // Should I read from NSUserDefaults here right after saving and then reloadData()?
 }

通常如何处理？

谢谢

答

基本上是正确的，但是如果删除了某些内容，则只应保存用户默认设置。

Basically it's correct, but you should only save in user defaults if something has been deleted.

if editingStyle == UITableViewCellEditingStyle.Delete {
    array.removeAtIndex(indexPath.row)
    tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Automatic)
    let userDefaults = NSUserDefaults.standardUserDefaults()
    userDefaults.setObject(array, forKey: "myArrayKey")
}

不需要也不建议读回数组。

Reading the array back is not needed and not recommended.

在 cellForRowAtIndexPath 重用该单元格，您需要在Interface Builder中指定标识符。

In cellForRowAtIndexPath reuse the cell, you need to specify the identifier in Interface Builder.

let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)

数据源数组必须在上声明

The data source array must be declared on the top level of the class

var array = [String]()

然后在 viewDidLoad 中分配值并重新加载表视图。

then assign the value in viewDidLoad and reload the table view.

override func viewDidLoad() {
    super.viewDidLoad()

    let userDefaults = NSUserDefaults.standardUserDefaults()
    guard let data = userDefaults.objectForKey("myArrayKey") as? [String] else {
        return 
    }
    array = data
    tableView.reloadData()
}

在Swift / iOS中从UITableView删除行并从NSUserDefaults更新数组的正确方法

相关推荐