How to change Realm property to nullable?

Question

How to change CalendarEvent.notes to optional (nullable)?

class CalendarEvent: Object {
    @objc dynamic var date: String = ""
    @objc dynamic var notes: String = ""
    @objc dynamic var notification: String = ""
}

The Realm database is already populated with data. I want the notes property to be changed to nullable in the Realm database. If I try @objc dynamic var notes: String? = "" a runtime error appears stating Migration is required due to the following errors: - Property 'CalendarEvent.notes' has been made optional.

According to the Realm documentation, renaming a property during a migration is a way to acheive this. Is it possible to change this property to nullable and without renaming?

@Anbu.Karthik this causes a runtime error stating `Migration is required due to the following errors: - Property 'CalendarEvent.notes' has been made optional.` — krichards, Jan 23 '20 at 05:32
you have to update the schema version like` let configuration = Realm.Configuration(schemaVersion: 2)` — Kishan Bhatiya, Jan 23 '20 at 05:42
I am trying to perform this https://stackoverflow.com/a/48899642/10555547 but in Realm swift instead — krichards, Jan 23 '20 at 06:03
Please check : https://realm.io/docs/swift/latest/#migrations — Kishan Bhatiya, Jan 23 '20 at 06:15

score 1 · Accepted Answer · answered Jan 23 '20 at 17:22

You can just handle this in the migration block and using the same property name is fine. Here's the code that would migrate a non-optional first_name property to an optional first_name property.

The original object looks like this

class PersonClass: Object {
    @objc dynamic var first_name = ""

and then we change the property to optional

class PersonClass: Object {
    @objc dynamic var first_name: String? = nil

and here's the migration block to do that. The first version was 1 (with the non-optional first_name) and version 2 is has the updated object.

let vers = UInt64(2)
let config = Realm.Configuration( schemaVersion: vers, migrationBlock: { migration, oldSchemaVersion in
     print("oldSchemaVersion: \(oldSchemaVersion)")
     if (oldSchemaVersion < vers) {
        print("  performing migration")

        migration.enumerateObjects(ofType: PersonClass.className()) { oldItem, newItem in
            newItem!["first_name"] = oldItem!["first_name"]
         }
     }
 })

This will leave the existing data intact. We use this kind of migration all of the time as our app needs change.

This is not working for Int or Bool. How to make an Int or a Bool property nullable? — mefahimrahman, Nov 27 '22 at 07:33
Hi @mefahimrahman - it's been a couple of years since this post and Realm is now using Persisted vars instead of the objc, but an optional bool is defined as `@Persisted var value: Bool?` and an optional Int is `@Persisted var value: Int?`. Please see the documentation for [Supported Property Types](https://www.mongodb.com/docs/realm/sdk/swift/model-data/define-model/supported-types/#supported-property-types). We use bools and ints all the time so if it's not working for you, perhaps a posting a question with your code an a description of the issue would help. — Jay, Nov 27 '22 at 14:08

How to change Realm property to nullable?

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