如何通過關係設置實體屬性？

Question

我有以下實體和關係

我希望能夠設置一個運動有它的例程名關係的零結果，如果是有道理的？以便在日常實體形成時可以將其設置爲例程名稱。

我的問題是，你如何設置這種屬性？我想下面的代碼，但它會導致嚴重的崩潰：

userExercise.usersroutine?.name = nil 

我的邏輯是，我走鍛鍊，並按照名稱屬性之間的關係，並將其設置爲nil？

感謝您的任何修正和澄清我的邏輯

編輯：添加我現有的鍛鍊和日常保存功能

func createExercise() { 
    guard let managedObjectContext = managedObjectContext else { return } 
    if let userExercise = userExercise { 
     userExercise.name = userExerciseName.text 
     userExercise.sets = Int64(userSetsCount) 
     userExercise.reps = Int64(userRepsCount) 
     userExercise.weight = Double(self.userExerciseWeight.text!)! 
     userExercise.id = UUID().uuidString 
     userExercise.routine = nil 
    } 
    do { 
     try managedObjectContext.save() 
    } catch { 
     fatalError("Failure to save context: \(error)") 
    } 
} 

例程創建：

func createRoutine() { 

    guard let managedObjectContext = managedObjectContext else { return } 
    let userRoutine = UserRoutine(context: managedObjectContext) 
    userRoutine.name = workoutNameTextfield.text 

    do { 
     try managedObjectContext.save() 
    } catch { 
     fatalError("Failure to save context: \(error)") 
    } 
} 

當前獲取請求：

fileprivate lazy var fetchedResultsController: NSFetchedResultsController<UserExercise> = { 

    let fetchRequest: NSFetchRequest<UserExercise> = UserExercise.fetchRequest() 
    fetchRequest.sortDescriptors = [NSSortDescriptor(key: "id", ascending: true)] 
    let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil) 
    fetchedResultsController.delegate = self 
    return fetchedResultsController 

Answer 1

請檢查下面的實現我已經創建了一些練習和例程。還請閱讀代碼中的評論，這將幫助您瞭解如何去做。

功能添加一個新的鍛鍊

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") 
    } 
} 

功能添加一個新的常規

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") 
     } 

} 

函數來獲得主要的NSManagedObjectContext上，我們可以進行核心數據的操作

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

下面，首先我創建一些與例程無關的練習

「例行犯規存在創建練習的時候，它之後創建的，其名稱設置爲」

，然後通過一些練習（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 
    } 

創建例程

更新創建例程查詢UserExercise的用戶程序結果爲零的功能

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)") 
     } 
    } 

Answer 2

似乎並不需要完全使用name屬性。該屬性應該用於存儲UserRoutine的實際名稱，而不是基於任何關係。

Core Data中實體之間的關係不依賴於實體的特定屬性，而是依賴於實體本身之間的關係。

「我想常規建設者看看練習並導入所有零練習的關係到它」

所以......

創建一個讀取請求取所有UserExercise的實體沒有相關的UserRoutine（即userroutine爲零）。

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

執行該讀取請求獲得UserExercises數組（沒有相關的例程）

let orphanedExercises = managedObjectContext.executeFetchRequest(orphanedExerciseFetchRequest()) 

將獲取UserExercise 「與歸屬演習創造一個例行」 entitiy的財產userRoutine到您的日常（並且不要忘記將更改保存在您的託管對象上下文中）。

myRoutine.userexercises = orphanedExercises 

以後，如果你想獲得一個特定的例行演習：

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