How to delete all data from core data when persistentContainer is not in App delegate method in swift

Question

I am new in Swift and I want to delete all data from core data. I have seen several examples but in all of them persistentContainer is in AppDelegate and in my case persistentContainer is not in AppDelegate. It is in a different class as shown below:

class CoreDataStack: NSObject {
    
    static let sharedInstance = CoreDataStack()
    private override init() {}
    
    func applicationDocumentsDirectory() {
        if let url = FileManager.default.urls(for: .libraryDirectory, in: .userDomainMask).last {
            print(url.absoluteString)
        }
    }
    lazy var persistentContainer: NSPersistentContainer = {
       
        let container = NSPersistentContainer(name: "Database")
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
            print(storeDescription)
            
        })
        return container
    }()
    
    // MARK: - Core Data Saving support
    
    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
}

In the AppDelegate method I am just calling it as

CoreDataStack.sharedInstance.applicationDocumentsDirectory()

func applicationWillTerminate(_ application: UIApplication) {
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
        CoreDataStack.sharedInstance.saveContext()
    }

I tried this code but it does not work for me.

pawello2222 · Accepted Answer · 2020-05-30T12:32:44.747

10

One of the solutions can be to use NSBatchDeleteRequest for all entities in the persistentContainer. You can add these methods to your CoreDataStack:

func deleteAllEntities() {
    let entities = persistentContainer.managedObjectModel.entities
    for entity in entities {
        delete(entityName: entity.name!)
    }
}

func delete(entityName: String) {
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
    do {
        try persistentContainer.viewContext.execute(deleteRequest)
    } catch let error as NSError {
        debugPrint(error)
    }
}

The whole code can be found here

edited May 30 '20 at 12:32

answered May 30 '20 at 12:21

pawello2222

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How can I used this? – Muju May 30 '20 at 12:22
showing used of Use of unresolved identifier 'managedObjectModel' Use of unresolved identifier 'persistentStoreCoordinator' – Muju May 30 '20 at 12:24
showing this error Value of type 'NSPersistentContainer' has no member 'execute' – Muju May 30 '20 at 12:30
How can I call this method where I need. And How to pass entity name in it – Muju May 30 '20 at 12:37
You can call it from anywhere in your project: `CoreDataStack.sharedInstance.deleteAllEntities()` – pawello2222 May 30 '20 at 12:38
It will delete whole database? – Muju May 30 '20 at 12:39
Yes, isn't it what you asked: `How to delete all data from core data`? – pawello2222 May 30 '20 at 12:40
correct but what if I only want to delete single entity. – Muju May 30 '20 at 12:41
Then if your entityName is `SomeModel` you can do: `CoreDataStack.sharedInstance.delete(entityName: "SomeModel")` – pawello2222 May 30 '20 at 12:43
perfect thanks a lot you save my day. Really thank you. – Muju May 30 '20 at 12:44

score 3 · Answer 2 · answered Aug 08 '22 at 05:27

Need to use NSBatchDeleteRequest for particular entity from persistentContainer

func deleteEntityData(entity : String) {
        let deleteFetch = NSFetchRequest<NSFetchRequestResult>(entityName: entity)
        let deleteRequest = NSBatchDeleteRequest(fetchRequest: deleteFetch)
        do {
            try CoreDataStack.sharedStack.mainContext.execute(deleteRequest)
            CoreDataStack.sharedStack.saveMainContext()
        } catch {
            print ("There was an error")
        }
}

I have detailed an answer in below link. enter link description here

score 0 · Answer 3 · answered Aug 10 '22 at 10:33

A more radical approach is to remove/recreate your persistent stores.

extension NSPersistentContainer {
    func destroyPersistentStores() throws {
        for store in persistentStoreCoordinator.persistentStores {
            let type = NSPersistentStore.StoreType(rawValue: store.type)
            try persistentStoreCoordinator.destroyPersistentStore(at: store.url!, type: type)
        }
        loadPersistentStores()
    }
    
    func loadPersistentStores() {
        loadPersistentStores { _, error in
            if let error { fatalError(error.localizedDescription) }
        }
    }
}

Usage: try container.destroyPersistentStores()

Source

How to delete all data from core data when persistentContainer is not in App delegate method in swift

3 Answers3