ios - 类型 'Self.ManageableType' 的值没有成员 'uid'

Question

这是我的代码，它是在 XCode 7.2.1 中构建的。当我尝试在 XCode 7.3 beta 2 中构建项目时，出现错误“‘Self.ManageableType’类型的值没有成员‘uid’”

protocol Manageable {
  typealias ManageableType : NSManagedObject
  var uid: String { get set }
}

extension Manageable {

  static func className() -> String {
    return String(self)
  }

  static func fetchObjects(predicate: NSPredicate?,
    completion:(fetchedObjects: [String: ManageableType]) -> ()) {
      let entityDescription = NSEntityDescription.entityForName(className(),
        inManagedObjectContext: CoreDataStack.sharedInstance.context)
      let fetchRequest = NSFetchRequest()
      fetchRequest.entity = entityDescription
      if let p = predicate {
        fetchRequest.predicate = p
      }
      var fetchedObjectsDict: [String: ManageableType] = [:]
      do {
        let result = try CoreDataStack.sharedInstance.context.executeFetchRequest(fetchRequest) as! [ManageableType]
        if result.count > 0 {
          for object in result {
            fetchedObjectsDict[object.uid] = object
          }
        }
      } catch {
        print("ERROR FETCH MANAGEABLE OBJECTS: \(error)")
      }
      completion(fetchedObjects: fetchedObjectsDict)
  }
}

当我尝试将循环代码块更改为:

for object in result {
    let uid = object.valueForKey("uid") as! String
    fetchedObjectsDict[uid] = object
}

我收到错误消息“‘valueForKey’的使用不明确”

为什么在新的 XCode 版本中会出现这些错误，请帮忙？

Answer 1

你的协议(protocol)扩展需要一个类型约束

extension Manageable where Self : NSManagedObject, ManageableType == Self { ... }