CoreData + Swift 2：多对多关系不适用于三张表

Question

这是我的问题。

我正在使用Xcode 7.3.1上的Core Data，Swift 2。我有3张桌子。第一个名为TableX，下一个是TableY，最后是TableZ，每个人都有它们的属性。 TableX没有任何关系，TableY与TableX的关系是“To Many”且没有相反的关系;而TableZ与TableY的关系“To Many”与相反。之后，我生成我的NSManagedObject子类。

我在TableX中添加了4个元素，然后我在TableY中添加了1个与TableX中的4个元素相关的寄存器，然后我在TableZ中添加了2个元素，每个元素与TableY中的寄存器相关。当我这样做时，TableX中的元素不会出现在TableZ的第一个寄存器中，而是出现在第二个寄存器中，TableZ中的两个寄存器都正确保存了TableY中的寄存器。为什么发生这种事我添加了我的代码。

func addElementToTableX(idEleX: String)->TableX?{ 
    let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext 

    let fetchRequestTableX = NSFetchRequest(entityName: "TableX") 
    let predicateTableX = NSPredicate(format: "tablexid == %@", idEleX) 
    fetchRequestTableX.predicate = predicateTableX 
    do { 
     let fetchedEntitiesTableX = try managedObjectContext.executeFetchRequest(fetchRequestTableX) as! [TableX] 
     if (fetchedEntitiesTableX.count == 0){ 
      let newTableX = NSEntityDescription.insertNewObjectForEntityForName("TableX", inManagedObjectContext: managedObjectContext) as! TableX 

     newTableX.tablexid = "saldkjadkj" 
     do { 
      try newTableX.managedObjectContext!.save() 
      print("Saved!") 
      return newTableX 
     } catch let error as NSError { 
      print("Error") 
      return nil 
     } 
     }else{ 
      print("This element exist") 
      return fetchedEntitiesTableX[0] 
     } 
    } catch { 
     return nil 
    }    
} 


func addElementToTableY(idEleY: String, elementsTableX: [TableX])->TableY?{ 
    let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext 

    let fetchRequestTableY = NSFetchRequest(entityName: "TableY") 
    let predicateTableY = NSPredicate(format: "tableyid == %@", idEleY) 
    fetchRequestTableY.predicate = predicateTableY 
    do { 
     let fetchedEntitiesTableY = try managedObjectContext.executeFetchRequest(fetchRequestTableY) as! [TableY] 
     if (fetchedEntitiesTableY.count == 0){ 
      let newTableY = NSEntityDescription.insertNewObjectForEntityForName("TableY", inManagedObjectContext: managedObjectContext) as! TableY 

     newTableY.tableyid = "ccbnnzmz" 
     newTableY.setValue(NSSet(array: elementsTableX), forKey: "tableX") 
     do { 
      try newTableY.managedObjectContext!.save() 
      print("Saved!") 
      return newTableY 
     } catch let error as NSError { 
      print("Error") 
      return nil 
     } 
     }else{ 
      print("This element exist") 
      return fetchedEntitiesTableY[0] 
     } 
    } catch { 
     return nil 
    }    
} 

func addElementToTableZ(idEleZ: String, elementsTableY: [TableY])->TableZ?{ 
    let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext 

    let fetchRequestTableZ = NSFetchRequest(entityName: "TableZ") 
    let predicateTableZ = NSPredicate(format: "tablezid == %@", idEleZ) 
    fetchRequestTableZ.predicate = predicateTableZ 
    do { 
     let fetchedEntitiesTableZ = try managedObjectContext.executeFetchRequest(fetchRequestTableZ) as! [TableZ] 
     if (fetchedEntitiesTableZ.count == 0){ 
      let newTableZ = NSEntityDescription.insertNewObjectForEntityForName("TableZ", inManagedObjectContext: managedObjectContext) as! TableZ 

     newTableZ.tablezid = "ccbnnzmz" 
     newTableZ.setValue(NSSet(array: elementsTableZ), forKey: "tableZ") 
     do { 
      try newTableZ.managedObjectContext!.save() 
      print("Saved!") 
      return newTableZ 
     } catch let error as NSError { 
      print("Error") 
      return nil 
     } 
     }else{ 
      print("This element exist") 
      return fetchedEntitiesTableZ[0] 
     } 
    } catch { 
     return nil 
    }    
} 

Answer 1

我建议神奇记录库。它会基于关键值编码工作，所以我们可以使用这个库实现多对多的关系。