Conditionally delete schema instead of migrating

Question

Realm has two approaches to handling schema changes:

Run a migration block, or
Drop the schema

Option 2 is not desired in our case, because we have a lot of data, our schema version is tied to the build number, and we release frequently.

So we use option 1. But some cases, it would be handy to run option 2 instead of migrating if the old schema version is too old. Is this possible?

Use case 1: I want to rename an Object class, but I don't want to risk botching the migration (which is easy to do). I'm fine with dropping the schema for users migrating from the version before the rename, but I don't want to keep on dropping the schema for subsequent migrations.

Use case 2: I've been writing migrations since 2016 (!), but I only really care about running migrations (rather than dropping the schema) for users who update regularly. So I'd like to maintain up to a few months' worth of migrations, and just drop the schema for anyone upgrading from before then.

I could probably hack together a workaround if I could figure out how to access my realm's old schema version before applying the configuration, but it seems like the only space in which Realm lets me see the schema version is in the migration block, and it doesn't seem like it's possible to decide to drop the schema when you're already running a migration.

Jay · Accepted Answer · 2020-08-11 20:58:06Z

1

This doesn't exactly answer the question but may lead to more complete solution.

If you need to retrieve the schema version of a realm file, here's how to do it (for the default config)

let x = try! schemaVersionAtURL(Realm.Configuration.defaultConfiguration.fileURL!)

and that documented in the API under Functions: schemaVersionAtURL(_:encryptionKey:)

answered Aug 11, 2020 at 20:58

Jay

35.8k19 gold badges61 silver badges89 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Phlippie Bosman Over a year ago

This perfectly answers the last part of my question - how to access my realm's old schema version before applying the configuration. Thanks!

Collectives™ on Stack Overflow

Conditionally delete schema instead of migrating

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related