在Swift中仅初始化一次CoreData实体

Question

I'm quite new to using CoreData in Swift and I wanted to create a persistent grade manager for learning purposes.

My class structure is as follows: I have a 'Student' entity in my CoreData with a to-many relationship with a 'Course' entity (with a to-many relationship with a 'Grade' entity).

I want to initialize a student at first startup automatically, so the user only has to add courses and grades, but I can't find out how to do so.

I currently have the initializer in my viewDidLoad() but that basically means it gets created a lot of times.

What's the solution to my problem?

Answer 1

If i am understanding it correctly, you want only 1 entity of student. Also putting initialiser code in viewDidLoad wont be called multiple times in a single run of the application.

Sure every time you launch the application, a new student will be created.

It has a very basic and easy workaround, which revolves around the concept of fetching and creating.

Follow these steps mentioned in the pseudocode :

 methodCreateOfFetchStudent(){
         1. Search Core data for any student entity.
         2. if found then return that studend (there will be only 1 found)
         3. If No student entity is found (array.count == 0) , then create a student with initialisation code.
         4. return that newly created student entity.
  } 

So for the first time when your application stats, in step 2, no student will be found, and it will create a student and return you the entity. Afterwards in each run, the method will return the old created student every time.

I hope I understood your requirement and this helped you.