NSManagedObject子类不确认协议

Question

我有NSManagedObject个子类，我希望他们确认我的自定义协议JSONInitializable 有我的协议：

protocol JSONInitializable {
  static func getAllEntities <T: NSManagedObject>(persistenceController:  PersistenceController) -> [T]
}

我的NSManagedObject子类函数导致错误：

class CDShipment: NSManagedObject, JSONInitializable {    
class func getAllEntities(persistenceController: PersistenceController) -> [CDShipment] {
  let request = NSFetchRequest(entityName: "CDShipment")
  let sorter = NSSortDescriptor(key: "managedNumber", ascending: true)
  request.sortDescriptors = [sorter]
  do {
    let results = try persistenceController.mainMoc?.executeFetchRequest(request) as! [CDShipment]
    return results
} catch {
    print("Error while getting all CDShipments")
  return []
 }
}
}

错误：

1. 协议要求函数'getAllEntities'的类型为'（PersistenceController） - ＆gt; [T]'（又名'＆lt;τ_1_0＆gt; PersistenceController - ＆gt;数组＆lt;τ_1_0＆gt;'）

2. 候选人具有非匹配类型'（PersistenceController） - ＆gt; [T]'（又名'＆lt;τ_0_0＆gt; PersistenceController - ＆gt;数组＆lt;τ_0_0＆gt;'）

我无法理解，问题是什么。