Core Data: Add a column on a table

Question

I just want to add a column on a table for my new version of my app, and keep the filled columns. So I work with Core Data, this is my momd:

On my appDelegate:

/* CORE DATA */

// MARK: - Core Data stack

lazy var applicationDocumentsDirectory: NSURL = {
    let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
    return urls[urls.count-1]
}()

lazy var managedObjectModel: NSManagedObjectModel = {
    let modelURL = NSBundle.mainBundle().URLForResource("solutis", withExtension: "momd")!
    return NSManagedObjectModel(contentsOfURL: modelURL)!
}()

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
    let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("solutis.sqlite")
    var failureReason = "There was an error creating or loading the application's saved data."
    do {
        try coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
    } catch let error as NSError {
        var dict = [String: AnyObject]()
        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
        dict[NSLocalizedFailureReasonErrorKey] = failureReason
        dict[NSUnderlyingErrorKey] = error
        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
        NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
        abort()
    } catch {
        fatalError()
    }

    return coordinator
}()


lazy var managedObjectContext: NSManagedObjectContext = {
    let coordinator = self.persistentStoreCoordinator
    var managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
    managedObjectContext.persistentStoreCoordinator = coordinator
    return managedObjectContext
}()

// MARK: - Core Data Saving support

func saveContext () {
    if managedObjectContext.hasChanges {
        do {
            try managedObjectContext.save()
        } catch {
            let nserror = error as NSError
            NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
            abort()
        }
    }
}

So if the user update the app with a filled table, he gonna keep the data and have the new version of the table.

But how to do ? I juste learned to add Model version, but how to retrieve old data ?

Apple provides a "Core Data Model Versioning and Data Migration Programming Guide" which should cover all that stuff. You should also find some tutorials about "Core Data migration". — Martin R, Sep 07 '16 at 13:10
Reading the Core Data Guide is good advice (see @MartinR). If you read it you will remember the option `NSMigratePersistentStoresAutomaticallyOption` with `NSPersistentStore`. It is necessarily required to switch it on. Renaming of columns is good for _Lightweight Migration_. No trouble to be expected. Adding a new column could be more challenging (e.g. if constraints does not allow empty values and no default value is given). Bear in mind: under the hood only [ALTER TABLE statements](https://www.sqlite.org/lang_altertable.html) and others will be performed, no magic ... — , Sep 10 '16 at 14:44

Core Data: Add a column on a table

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