How to do Abstract Entities in Realm.io in Swift - ios

Question

I am converting from CoreData to Realm.io I did a little experiment to see how Realm.io handles situations where I need to have subclasses of a class that is an RLMObject.
Model
import Realm
#objc enum RecurrenceEnum : Int {
case Daily = 1
case Weekly = 2
case Monthly = 3
}
class Challenge: RLMObject {
dynamic var title = ""
}
class TotalCountChallenge: Challenge {
dynamic var totalCountGoal: Int = 0
}
class RecurringChallenge: Challenge {
dynamic var recurranceType: RecurrenceEnum = .Daily
dynamic var totalCountGoal: Int = 0
}
When I save either a TotalCountChallenge or A RecurringChallenge it reports no errors but when I go to query for challenges by title I don't get anything back.
Query from my ViewController
// Query using an NSPredicate object
let predicate = NSPredicate(format: "title BEGINSWITH %#", "Booya")
var challenges = Challenge.objectsWithPredicate(predicate)
if challenges == nil || challenges.count == 0 {
let tcChallenge = TotalCountChallenge()
tcChallenge.title = "Booya Total Count Challenge"
tcChallenge.totalCountGoal = 1_000_000
let rChallenge = RecurringChallenge()
rChallenge.title = "Booya Recurring Challenge"
rChallenge.recurranceType = .Weekly
rChallenge.totalCountGoal = 2_000_000
let realm = RLMRealm.defaultRealm()
// You only need to do this once (per thread)
// Add to the Realm inside a transaction
realm.beginWriteTransaction()
realm.addObject(tcChallenge)
realm.addObject(rChallenge)
realm.commitWriteTransaction()
}
challenges = Challenge.objectsWithPredicate(predicate)
if challenges != nil && challenges.count > 0 {
for challenge in challenges {
let c = challenge as! Challenge
println("\(c.title)")
}
} else {
println("No Challenges found")
}
challenges = TotalCountChallenge.objectsWithPredicate(predicate)
if challenges != nil && challenges.count > 0 {
for challenge in challenges {
let c = challenge as! Challenge
println("TotalCountChallenge: \(c.title)")
}
} else {
println("No Total Count Challenges found")
}
challenges = RecurringChallenge.objectsWithPredicate(predicate)
if challenges != nil && challenges.count > 0 {
for challenge in challenges {
let c = challenge as! Challenge
println("RecurringChallenge \(c.title)")
}
} else {
println("No Recurring Challenges found")
}
Output
No Challenges found
TotalCountChallenge: Booya Total Count Challenge
RecurringChallenge Booya Recurring Challenge
When I look at the database using the Browse Tool provided by Realm I see that there is only 1 TotalCountChallenge and 1 RecurringChallenge and there are no Challenges
Is there a way to do this?
Here is a link to the code in github: lewissk/RealmTest

Answer 1

Realm supports subclassing, but not the sort of polymorphism that you're looking for. In Realm, each object type is stored in its own table, regardless of whether or not you've declared it in code as a subclass of another object. The implication of this is that isn't not currently possible to query across different object classes, even if they share a common superclass. There's an issue tracking this feature request at https://github.com/realm/realm-cocoa/issues/1109.