[CoreData] #CoreData #SwiftUI #iOS

CoreDataManagerInit.swift

import Foundation
import CoreData

final calss CoreDataManger {
  
  let persistentContainer: NSPersistentContainer
  
  init() {
        ///To Initialize persistent container you have to pass in the file name of the model
        persistentContainer = NSPersistentContainer(name: "HelloCoreDataModel")
        ///Persistent Container has the Fields description and error
        persistentContainer.loadPersistentStores{ (description, error) in
            ///Error Handling
            if let error = error{
                fatalError("Core Data Store failed to initialize \(error.localizedDescription)")
            }
		}
  }
  
  //Functions you need to manage Data like Delete Save etc.
}

DeleteEntity.swift

func deleteMovie(movie: Movie) {
  //Mark for deletion
  persistentContainer.viewContext.delete(movie)
  
  //Delete through saving
  do {
    try persistent.Container.viewContext.save()
  } catch {
    persistent.Container.viewContext.rollback()
    print("Failed to save context \(error.localizedDescription)")
  }
}

DisplayingOneToMany.swift

func getReviewsByMovie(vm: MovieViewModel) {
  let movie = CoreDataManager.shared.getMovieById(id: vm.id)
  if let movie = movie {
    DispatchQueue.main.async{
      ///Get all Reviews and cast it into an array
      ///Map over it to make an instance of review for every element in the array
      ///assign it to self.reviews
      self.reviews = (movie.reviews?.allObjects as! [Review]).map(ReviewViewModel.init)
    }
  }
}

GettAllOfEntity.swift

func getAllMovies() -> [Movie] {
  //You can pass in the type you wan't to have in <TYPE> | The Movie class has already a fetch request we can pass in
  let fetchRequest: NSFetchRequest<Movie> = Movie.fetchRequest()
  
  //Returns the Fetched data with error handling
  do {
    return try persistentContainer.viewContext.fetch(fetchRequest)
  } catch{
    return []
  }
}