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Swift 2（executeFetchRequest）：错误处理

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19

我遇到了一些我无法弄清楚的代码问题 . 在我安装了Xcode 7 beta并将我的swift代码转换为Swift 2之后

Code:

override func viewDidAppear(animated: Bool) {

    let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate

    let context: NSManagedObjectContext = AppDel.managedObjectContext
    let request = NSFetchRequest(entityName: "PlayerList")

    list = Context.executeFetchRequest(request)

    tableView.reloadData()
}

ScreenShot:

enter image description here

swift swift2

5 回答

  • 3
    var results = [YourEntity]?
results = try! self.managedObjectContext!.executeFetchRequest(fetchRequest) as! [YourEntity]
    回复于
  • 1

    请尝试下面的代码

    override func viewWillAppear(animated: Bool) {

        let appDel:AppDelegate = (UIApplication.sharedApplication().delegate as! AppDelegate)
        let context = appDel.managedObjectContext
        let request = NSFetchRequest(entityName:"Users")
        do {
            let results = try context.executeFetchRequest(request)

            itemList = results as! [NSManagedObject]


        } catch let error as NSError {
            print("Could not fetch \(error), \(error.userInfo)")
        }


    }
    回复于
  • 54

    从Swift 2开始，产生错误的Cocoa方法被转换为抛出错误的Swift函数 .

    而不是_2617610中的可选返回值和错误参数：

    var error : NSError?
if let result = context.executeFetchRequest(request, error: &error) {
    // success ...
    list = result
} else {
    // failure
    println("Fetch failed: \(error!.localizedDescription)")
}

    在 Swift 2 中，该方法现在返回一个非可选项并在错误情况下抛出一个错误，必须使用try-catch处理：

    do {
    list = try context.executeFetchRequest(request)
    // success ...
} catch let error as NSError {
    // failure
    print("Fetch failed: \(error.localizedDescription)")
}

    有关详细信息，请参阅"Using Swift with Cocoa and Objective-C"文档中"Adopting Cocoa Design Patterns"中的"Error Handling" .

    回复于
  • 4

    你可以尝试这段代码：

    let  result = (try! self.manageContext.executeFetchRequest(FetchRequest)) as! [NSManageObjectClass]
    回复于
  • 1

    Swift 3.0 在此示例中 PlayerList 是 NSManagedObject 实体/类名称（由Xcode自动创建）

    let request: NSFetchRequest<PlayerList> = PlayerList.fetchRequest()

var result:[PlayerList]?
do{
      //Succes 
      result = try context.fetch(request)
   }catch let error as NSError {
      //Error 
      print("Error \(error)")
  }

print("result: \(result)")
    回复于

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