Question

我试图将我的Swift 1代码转换为Swift 2.1.1代码。所以我想添加一个fetchRequest。

在Swift 1中我这样做了：

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（第二次请求 - ＆gt;不起作用）：

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？谢谢你的帮助！

Answer 1

您可以将其打包在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)")
}

修改

第二次请求：

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)") }

在Swift 2.1.1中获取请求

1 个答案: