在Swift中獲取請求2.1.1

Question

我試圖將我的Swift 1代碼轉換爲Swift 2.1.1代碼。 所以我想添加一個fetchRequest。

在夫特1 I這樣做：

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)") 
    } 

夫特2.1（第二請求 - >不工作）：

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)") 
} 

錯誤管線（ 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

錯誤的行（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]?'

能否請你幫我翻譯成斯威夫特2.1.1嗎？ 感謝您的幫助！

Answer 1

您可以將其包裝在docatch塊中。如果let results行失敗，它將打印一個錯誤。

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)") 
} 

編輯

第二個請求：

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)") 
}