CoreData警告:多个NSEntityDescriptions声明NSManagedObject子类

我刚刚解决了同一个错误,即我对持久化容器使用了computed属性。因此,每次应用程序访问持久容器/存储时,都会从磁盘创建新的数据模型实例。

在我将persistent容器更改为惰性存储属性之后,问题就消失了。

[更新]

目前,我为核心数据堆栈使用一个单独的类,其中使用了如下单例:

class DataCtrl : NSObject {

static shared = DateCtrl()
var container: NSPersistentContainer?

private override init() { 
    container = NSPersistentContainer(name: "dataModelName")
}
func loadStore (completionHandler: @escaping () -> ()) {
self.container?.loadPersisentStores() { 
desc, err in ...
    completionHandler
    }
 }
}

然后我可以轻松地在tableViewController扩展中使用computed属性:

var container : persistentContainer { return DateCtrl.shared.container }

当然,您需要调用AppDelegate didffinishlaunchingwithoptions块中的func load store首先加载持久存储,在completionHandler中使用DispatchGroup()来控制加载第一个视图控制器的数据模型。

我想出了解决办法。必须在单元测试类中创建一个NSEntityDescription实例,并在每次创建与实体描述匹配的对象时重用它。在下面的代码中,查看setup、tearDown和testFetchPerson()

   var container: NSPersistentContainer!

   **var entityDescription: NSEntityDescription! // Insert only one instance into your managed object context * see setup//**

   override func setUp() {
       super.setUp()
       let bundle = Bundle(for: type(of: self))
       let url = bundle.url(forResource: "DivyaPracticeWorkspace", withExtension: "momd")!
       let managedObjectModel = NSManagedObjectModel(contentsOf: url)!
       container = NSPersistentContainer(name: "testContainer", managedObjectModel: managedObjectModel)
       let description = NSPersistentStoreDescription()
       description.type = NSInMemoryStoreType
       container.persistentStoreDescriptions = [description]
       container.loadPersistentStores(completionHandler: { (description, error) in
           if let error = error {
               print("\(error)")
           }
       })

       mockCoreData = CoreDataManager(container: container)
**// Insert only one entity description into the context
       entityDescription  = NSEntityDescription.entity(forEntityName: "Person", in: mockCoreData.mainContext)!**
   }


   override func tearDown() {
       super.tearDown()
       deleteAllObjects()
       mockCoreData = nil
       container = nil
   }

   private func deleteAllObjects() {
       let request: NSFetchRequest<Person> = Person.fetchRequest()
       do {
           let results = try mockCoreData.mainContext.fetch(request)
           for entry in results {
               mockCoreData.mainContext.delete(entry)
           }

           mockCoreData.saveChanges {
               [weak self] in
               guard let this = self else {
                   return
               }

               this.mockCoreData.mainContext.refreshAllObjects()
               this.mockCoreData.mainContext.reset()
               guard let store = this.container.persistentStoreCoordinator.persistentStores.first else {
                   return
               }
               do {
                   try this.container.persistentStoreCoordinator.remove(store)
               } catch let error {
                   print("\(error)")
               }
           }
       } catch let error {
           print("\(error)")
       }
   }

   func testFetchPerson() {
        var fetchSuccess = false
**// Create person entity using the entity description created in setup.
           let personEntity = Person(entity: entityDescription, insertInto: mockCoreData.mainContext)**

           personEntity.name = "Bob"
           personEntity.gender = Int32(0)

           mockCoreData.saveChanges(completion: nil)


           if let personFetched = mockCoreData.fetchPerson(name: "Bob")?.first {
               fetchSuccess = personFetched.gender == Int32(0) && personFetched.name == "Bob"
           }
       XCTAssertTrue(fetchSuccess)
   }