Concurrency Core Data Stack

core_data_stack.swift

class CoreDataHelper {

    // MARK: - Core Data Stack
	
    lazy var applicationDocumentsDirectory:  URL  = {
        let urls =  FileManager.default.urls(for: .documentDirectory,  in: .userDomainMask)
	return urls[urls.count-1]
    }()

    lazy var managedObjectModel:  NSManagedObjectModel  = {
        let modelURL =  Bundle.main.url(forResource:  "app_name", withExtension:  "momd")!
	return NSManagedObjectModel(contentsOf: modelURL)!
    }()

    lazy var persistentStoreCoordinator:  NSPersistentStoreCoordinator  = {
        var coordinator =  NSPersistentStoreCoordinator(managedObjectModel:  self.managedObjectModel)
	let url =  self.applicationDocumentsDirectory.appendingPathComponent("SingleViewCoreData.sqlite")
	let options =  [NSMigratePersistentStoresAutomaticallyOption:  true, NSInferMappingModelAutomaticallyOption:  true]

      	do {
	   try coordinator.addPersistentStore(ofType:  NSSQLiteStoreType, configurationName:  nil, at: url, options: options)
        } catch {
            print(erorr)
        }

	return coordinator
    }()

    lazy var mainObjectContext:  NSManagedObjectContext  = {
        let coordinator =  self.persistentStoreCoordinator
	
	var managedObjectContext =  NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
		
        // set the coordinator
        managedObjectContext.persistentStoreCoordinator = coordinator

        // This policy discards in-memory state changes for objects in conflict. 
              // The persistent store’s version of the objects’ state is used
        managedObjectContext.mergePolicy =  NSRollbackMergePolicy  

        return managedObjectContext
    }()

    /// Creates a new private context from the current state of `managedObjectContext`
    func generatePrivateContext() -> NSManagedObjectContext {
        // Initialize Managed Object Context
        let managedObjectContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
        
        // Configure Managed Object Context
        managedObjectContext.parent = self.managedObjectContext
        
        return managedObjectContext
    }
}