Swift 2.1.1 中的获取请求

Question

我正在尝试将我的 Swift 1 代码转换为 Swift 2.1.1 代码。所以我正在尝试添加一个 fetchRequest。

在 Swift 1 我这样做了：

if let results = context.executeFetchRequest(fetchRequest, error:&error), 
   let managedObject = results.first as? NSManagedObject {
       context.deleteObject(managedObject)
    }

let saveError: NSError?
context.save(nil)

和

 var error: NSError?
 let fetchedResults = managedContext.executeFetchRequest(fetchRequest) as! [NSManagedObject]?
 if let results = fetchedResults {
      people = results
   } 
   else {
      print("Could not fetch \(error), \(error!.userInfo)")
   }

Swift 2.1（第二个请求 -> 无效）：

do {
  let fetchedResults = try managedContext.executeFetchRequest(fetchRequest) as! [NSManagedObject]
   // success if it gets here
   if let results = fetchedResults {
        people = results
    }
 } catch let error as NSError {
    // failed so print error
    print("Error: \(error.localizedDescription)")
 }

行中的错误 (if let results... & let fetchedResults...)：

Initializer for conditional binding must have Optional type, not '[AnyObject]'

Call can throw, but is not marked with 'try' and the error is not handled

行中的错误 (let fetchedResults...)：

Call can throw, but is not marked with 'try' and the error is not handled

Cannot downcast from '[AnyObject]' to a more optional type '[NSManagedObject]?'

你能帮我把它翻译成Swift 2.1.1吗？感谢您的帮助！

Answer 1

您可以将其包装在 do catch 块中。如果 let results 行失败，它将打印错误。

do {
    let results = try context.executeFetchRequest(fetchRequest)
    // success if it gets here
    if let managedObject = results.first as? NSManagedObject {
        context.deleteObject(managedObject)
    }
} catch let error as NSError {
    // failed so print error
    print("Error: \(error.localizedDescription)")
}

编辑

第二个请求：

do {
  let fetchedResults = try managedContext.executeFetchRequest(fetchRequest)
   // success if it gets here
   if let results = fetchedResults as? [NSManagedObject]{
        people = results
    }
 } catch let error as NSError {
    // failed so print error
    print("Error: \(error.localizedDescription)")
 }

Swift 2.1.1 中的获取请求

Fetch request in Swift 2.1.1

core-data

swift

xcode7

swift2