CODEWITHSUNDEEP
iosswiftcore-data
Cam Connor
Cam Connor

Reputation: 1231

CoreData not returning any rows

I'm trying to make it so that when the user logs out of my app the CoreData is wiped with the function below.

func wipeMessagesFromDB(){
    let moc = managedObjectContext

    var array = [cdMessageMO]()

    let messageFetch: NSFetchRequest<cdMessageMO> = NSFetchRequest(entityName: "Message")

    do {
        array = try moc.fetch(messageFetch as! NSFetchRequest<NSFetchRequestResult>) as! [cdMessageMO]//this isnt working!
        for managedObject in array
        {
            let managedObjectData:NSManagedObject = managedObject as NSManagedObject
            managedObjectContext.delete(managedObjectData)
        }
    } catch {
        fatalError("Failed to fetch attractions: \(error)")
    }
}

The problem is if I call the function when the user logs out, the array length is 0 so nothing is wiped. This is bad because the length shouldn't be 0. I'm 100% there are entries that should be returned because if I call the same function on startup the array is populated.

Any ideas on what's causing this?

Upvotes: 0

Views: 44

Answers (1)

MathewS
MathewS

Reputation: 2307

Message fetch has the signature NSFetchRequest<cdMessageMO>

let messageFetch: NSFetchRequest<cdMessageMO>

But then you're force casting to NSFetchRequest<NSFetchRequestResult>

array = try moc.fetch(messageFetch as! NSFetchRequest<NSFetchRequestResult>) as! [cdMessageMO]

I'm pretty sure that will always fail (?)

Also, if you're not doing anything with the messages (just want to delete them) you can use the batch delete which is faster because it doesn't actually load the objects into memory:

let context = managedObjectContext

let fetch = NSFetchRequest(entityName: "Message")
let delete = NSBatchDeleteRequest(fetchRequest: fetch)

do {
    try myPersistentStoreCoordinator.executeRequest(delete, withContext: context)
} catch {
    // handle the error
}

Upvotes: 1

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