RealmCollection interface

[cmelchior]

We need a RealmCollection to be able to parse different lists into UI components.

• Figure out exactly which methods should be in the interface
• Make RealmResults and RealmList implement the interface
• Document the interface on the website (Explain what a Realm collection is and how it is used. #2258).

v1 Needs to support RealmResults and RealmList /cc #972
v2 Support for RealmSet when it becomes available #759
v3 Support for RealmMap. Will most likely require its own interface. #759

[bmunkholm]

Align with Cocoa on this.

[cmelchior]

I think we could split this into possible 2 interfaces. The reason being that our observer pattern is being reused across all our primary classes.

public interface RealmObservable {
  void addChangeListener(ChangeListener listener);
  void removeChangeListener(ChangeListener listener);
  void removeAllChangeListeners();
}

public interface RealmCollection<E> extends List<E>, RealmObservable {
  boolean isLoaded();
  E load();
}

What do you think? @realm/java

[dalinaum]

I am worry about little confusing between RxJava's Observable and proposed Observable.

[saket]

I so need this for an adapter that is capable for handling both RealmList and RealmResults :D

[cmelchior]

@dalinaum True, Observable was just my initial suggestion. RealmObservable could probably also work. I updated the proposal

[cmelchior]

Looking at RLMCollection: https://realm.io/docs/objc/latest/api/Protocols/RLMCollection.html, it seems our RealmCollection interface should be the following:

// All collections are Lists. This won't work with Sets, problem?
public interface RealmCollection<E> extends List<E>, RealmObservable {
  E first()
  E last() // we don't have this currently
  RealmQuery<E> where()
  Number min(String field)
  Number max(String field)
  Number sum(String field)
  Number average(String field)
  Date maxDate(String field)
  Date minDate(String field)

  // Async methods
  boolean isLoaded();
  E load();

  // These are kinda new. Didn't we remove those for some reason?
  RealmCollection<E> sort(String field, Sort sortOrder)
  RealmCollection<E> sort(String field1, Sort sortOrder1, String field2, Sort sortOrder2)
  RealmCollection<E> sort(String[] fields, Sort[] sortOrders)
}

[cmelchior]

@kneth / @emanuelez Didn't we remove RealmResults.sort() for some reason?

[jpsim]

This is an area where the Swift API has gotten a little further ahead than the ObjC one: https://realm.io/docs/swift/latest/api/Protocols/RealmCollectionType.html

We expose aggregate operations on all RealmCollectionTypes: min, max, sum, average.

Otherwise, judging by what you inherit when you extend List, it seems to cover everything.

[beeender]

And maybe try to align the behaviour of clear and removeFromRealm in the interface

[cmelchior]

Yes, having a unified RealmCollection interface means we have to find the same semantics for all methods as realmCollection.clear() should work the same way regardless if it a RealmResults or a RealmList.