Where to call freeze() when working with Realm collections and Combine?

Question

I'd like to display some Realm objects in a read-only view (SwiftUI), and as far as I've understood, Realm objects should be frozen for such views.

But where should I call .freeze()? On the Results-object or the publisher?

Realm().objects(Contact.self)
    .freeze()
    .publisher
    .[...]

vs.

Realm().objects(Contact.self)
    .publisher
    .freeze()
    .[...]

Or does it make no difference?

Answer 1

I've just tested both variants:

cancellable = try! Realm().objects(Contact.self)
    .freeze()
    .collectionPublisher
    .map { ... }
    .receive(on: DispatchQueue.main)
    .assertNoFailure()
    .assign(to: \.contacts, on: self)

vs.

cancellable = try! Realm().objects(Contact.self)
    .collectionPublisher
    .freeze()
    .map { ... }
    .receive(on: DispatchQueue.main)
    .assertNoFailure()
    .assign(to: \.contacts, on: self)

While both variants are compiling, the first won't work: Terminating app due to uncaught exception 'RLMException', reason: 'Frozen Realms do not change and do not have change notifications.'

Therefore freeze() has to be called on the publisher.