如何通过关系设置实体属性？

2 回答

• 1

  请检查下面的实现我已经创建了一些练习和例程 . 同时阅读代码中的注释，这将帮助您弄清楚如何去做 .

  添加新练习的功能

  func createExercise(weight: Int16, respetitions: Int16, name: String, routine: Routine?)->Exercise? {
      let context = getMainContext()
      let exercise = NSEntityDescription.insertNewObject(forEntityName: "Exercise", into: context) as! Exercise
      exercise.setValue(weight, forKey: "weight")
      exercise.setValue(name, forKey: "name")
      exercise.setValue(respetitions, forKey: "rep")
  
      do {
          try context.save()
          return exercise
      }
      catch
      {
          fatalError("unable to Ssavve")
      }
  }
  

  添加新例程的功能

  func createRoutine(name: String, exercises:[Exercise]) {
      let context = getMainContext()
      let routine = NSEntityDescription.insertNewObject(forEntityName: "Routine", into: context) as! Routine
      routine.name = name
  
      //Iterate over Exercise objects & check if routine is nil. 
     //Here if routine is not nil it menas your exercise is already assigned to a routine. 
     //If routine is nil assign routine.addToRelationship(<#T##value: Exercise##Exercise#>) and Also assign routine to the execise.
  
       do {
              try context.save()
          }
          catch
          {
              fatalError("unable to Ssavve")
          }
  
  }
  

  获取主NSManagedObjectContext的函数，我们可以在其上执行核心数据操作

  func getMainContext() -> NSManagedObjectContext {
      let appDelegate = UIApplication.shared.delegate as! AppDelegate
      return appDelegate.persistentContainer.viewContext
  }
  

  下面，首先，我创建一些与例程没有任何关系的练习

  “创建练习时，例程不存在，之后创建，并设置其名称”

  然后通过传递一些练习来创建例程（You can refer to other answer on how to fetch exercises with routine as nil values）

  func initializer() {
          //I'm adding exercises first without routines
          let ex1 = self.createExercise(weight: 10, respetitions: 4, name: "Exercise1", routine: nil)
          let ex2 = self.createExercise(weight: 5, respetitions: 10, name: "Exercise2", routine: nil)
          let ex3 = self.createExercise(weight: 20, respetitions: 2, name: "Exercise3", routine: nil)
          let ex4 = self.createExercise(weight: 5, respetitions: 10, name: "Exercise2", routine: nil)
  
          self.createRoutine(name: "Routine 1", exercises: [ex1!, ex2!]) //You can pass all the exercises or use fetch request to query exercises with routine as nil
          self.createRoutine(name: "Routine 2", exercises: [ex3!, ex4!])
  
          self.createRoutine(name: "Routine 3", exercises: [ex1!, ex2!]) //This routine shall not be adding any execises as they are already added to othe routines
      }
  

  更新create routine函数以查询UserExercise的结果，其中usersroutine为nil

  func createRoutine() {
  
      guard let managedObjectContext = managedObjectContext else { return }
      let userRoutine = UserRoutine(context: managedObjectContext)
      userRoutine.name = workoutNameTextfield.text
  
  //Getting nil value User Exercises        
      let request: NSFetchRequest<UserExercise> = UserExercise.fetchRequest()
                  request.predicate = NSPredicate(format: "usersroutine == nil")
                  do {
                      let appDelegate = UIApplication.shared.delegate as! AppDelegate
                      let context = appDelegate.persistentContainer.viewContext
                      let queryResults = try context.fetch(request)
  
                      //I like to check the size of the returned results!
                      print ("num of results = \(queryResults.count)")
  
                      //You need to convert to NSManagedObject to use 'for' loops
                      for exercise in queryResults as [NSManagedObject] {
                          //get the Key Value pairs (although there may be a better way to do that...
                          print("Exercise NAME: \(exercise.value(forKey: "name"))")
                      }
                  } catch {
                      print("Error with request: \(error)")
                  }
  
  
          do {
              try managedObjectContext.save()
          } catch {
              fatalError("Failure to save context: \(error)")
          }
      }
  

  回复于 2024-04-25T18:48:35+08:00
• 0

  您似乎根本不需要使用 name 属性 . 此属性应用于存储 UserRoutine 的实际名称，而不是基于任何关系 .

  Core Data中的实体之间的关系不依赖于实体的特定属性，而是依赖于实体本身 .

  “我希望例程构建器查看练习并导入所有与nil关系的练习”

  所以...

  创建一个获取请求以获取 UserExercise 的所有没有相关 UserRoutine 的实体（即 userroutine 为零） .

  let orphanedExerciseFetchRequest = NSFetchRequest(entityName: "UserExercises")
  orphanedExerciseFetchRequest.predicate = NSPredicate(format: "userroutine == nil)
  

  执行此获取请求以获取UserExercises数组（没有相关例程）

  let orphanedExercises = managedObjectContext.executeFetchRequest(orphanedExerciseFetchRequest())
  

  “创建一个带有归因练习的例程”

  将获取的 UserExercise entitit属性 userRoutine 设置为例程（并且不要忘记在管理对象上下文中保存更改） .

  myRoutine.userexercises = orphanedExercises
  

  之后，如果您想要针对特定例程进行练习：

  let fetchRequest = NSFetchRequest(entityName: "UserExercises")
  fetchRequest.predicate = NSPredicate(format: "userroutine == %@", someUserRoutine)
  

  回复于 2024-04-25T18:48:35+08:00