Realm - Delete objects from realm in migration block

Question

I need to delete objects from a realm during a migration.

I have an AccountManager which contains :

func logOut() {
    let realm = try! Realm()
    try! realm.write {
        realm.delete(realm.objects(Account.self))
        realm.delete(realm.objects(Address.self))
        ... // Other deletions
    }
}

But whenever I use the logOut() function in a migration block it just fails.

    let config = Realm.Configuration(
        schemaVersion: 11,
        migrationBlock: { migration, oldSchemaVersion in
            if (oldSchemaVersion < 11) {
                // Delete objects from realm
                AccountManager().logOut() // DOESN'T WORK
            }
    })

    Realm.Configuration.defaultConfiguration = config

I absolutely need users to relog after this update - Is there any way I could perform these deletions in a migration block ?

kishikawa katsumi · Accepted Answer · 2016-11-07 14:39:23Z

18

You can use Migration.deleteData(forType typeName: String) instead Realm.delete(_:) as follows.

Realm.Configuration(schemaVersion: 11, migrationBlock: { migration, oldSchemaVersion in
    if oldSchemaVersion < 11
        migration.deleteData(forType: Account.className)
        migration.deleteData(forType: Address.className)
        ...

answered Nov 7, 2016 at 14:39

kishikawa katsumi

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1 Comment

milad salimi Over a year ago

Hi , please check my question about realm migration , stackoverflow.com/questions/59855380/…

shim · Accepted Answer · 2018-02-07 16:49:09Z

14

You can tell Realm to delete when migration needed.

Realm.Configuration.defaultConfiguration = Realm.Configuration(
    schemaVersion: 10,
    migrationBlock: { migration, oldSchemaVersion in


    },
    deleteRealmIfMigrationNeeded: true
)

edited Feb 7, 2018 at 16:49

shim

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answered Nov 2, 2016 at 19:56

wint

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3 Comments

nth Over a year ago

Is there any way I could specify this realm deletion only has to be applied when migrating from version 10 to 11 ?

wint Over a year ago

I never try that, I guess you have to write your own migration code. Check out this answer stackoverflow.com/a/40467810/2003085

haart Over a year ago

for deleting realm only when migrating from certain versions, check out github.com/realm/realm-js/issues/502#issuecomment-228058951

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