Alex Leffelman: Migrating to Realm on iOS

Transcript

1. Alex from Remind - alex@remindhq.com - @LeffelMania - remind.com/about
2. Try Before You Buy How to Test-Drive Realm Alongside Core Data
3. Gearing Up for a Realm Migration
4. Why Choose?
5. Remind’s Starting Point - RestKit - AFNetworking 1.x - Complicated RestKit mapping DSL - Mogenerator-generated model classes - Modular Remind stack on top of RestKit
6. Our Top Risk: Object Mapping into Realm - From-Scratch implementation - Inconsistent JSON data - Type coercion
7. Server-Side Kill-Switch + Monitoring
8. Parallel Databases - Server is the only source of truth - Hook into RestKit’s exit point - Map raw JSON into Realm database
9. Parallel Data Models: anti-DRY - User == RealmUser, Group == RealmGroup, etc - Determine migration lifetime early on
10. Integrating Initial UI Updates - Low-traffic, stable screens - Representative of general patterns - How to accommodate both model types? - Replication vs. Conditional Logic
11. Interoperability @interface RLMObject (CoreDataMatching) + (NSString *)coreDataEntityName; - (NSPredicate *)coreDataMatchingPredicate; - (id)coreDataEntity:(NSManagedObjectContext *)context; @end @interface NSManagedObject (RealmMatching) + (NSString *)realmEntityName; - (NSPredicate *)realmMatchingPredicate; - (id)realmEntity:(RLMRealm *)realm; @end
12. @implementation RLMObject (CoreDataMatching) - (NSPredicate *)coreDataMatchingPredicate { NSString *primaryKey = [[self class] primaryKey]; id primaryValue = [self valueForKeyPath:primaryKey]; return [NSPredicate predicateWithFormat:@"%K == %@", primaryKey, primaryValue]; }
13. @implementation NSManagedObject (RealmMatching) - (__kindof RLMObject)realmEntity:(RLMRealm *)realm { NSString *entityName = [[self class] realmEntityName]; Class entityClass = NSClassFromString(entityName); NSPredicate *predicate = [self realmMatchingPredicate]; RLMResults *results = [entityClass objectsInRealm:realm withPredicate:predicate]; return [results firstObject]; }
14. That’s It - Everything you need to migrate gradually.
15. Finishing the Job - What To Do/Not Do - With high confidence, dive in - Have a plan - Don’t underestimate
17. Non-Obvious, Non-Trivial Migration Tasks - Network replacement? - Supplementing Realm features - Unit Tests - Continuous integration - Code Review
18. Cutting Out Core Data - Press forward with Realm entities? - Abandon Realm entities and migrate Core Data?
19. The Wrong Process, AKA, “The Hal” - Update one class’s @interface to use Realm only. - Recurse every broken reference to that class - Follow the compiler until the build is green again
22. A Better Process(?) - 2 Steps Back = 100 Steps Forward - Remove your Realm entities - Convert your Core Data entities directly
23. #winning
24. Recap: - You can roll out a Realm migration slowly - Be safe out there - Don’t be an idiot like me - It’ll still take longer than you think
25. That’s it! Thanks, Realm! - alex@remindhq.com - @LeffelMania - remind.com/careers - Questions?