在Swift中获取请求2.1.1

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。

在夫特1 I这样做：

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（第二请求 - >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)") 
} 

错误管线（ 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

错误的行（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]?'

能否请你帮我翻译成斯威夫特2.1.1吗？ 感谢您的帮助！

Answer 1

您可以将其包装在docatch块中。如果let results行失败，它将打印一个错误。

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)") 
}