Add Realm.isEmpty property

[astigsen]

List and Results are missing the isEmpty() method as defined on the CollectionType Protocol.

It would also be really useful with an isEmpty() method on the Realm object, to show if it contains any objects at all.

[segiddins]

isEmpty() has a default implementation that just checks the count

[jpsim]

That's right. If the Swift standard library has a function that works with Realm types and reimplementing it ourselves wouldn't offer any performance improvements, we don't reimplement it.

Free function in Swift 1.2: http://swiftdoc.org/func/isEmpty/

CollectionType extension in Swift 2.0: http://swiftdoc.org/swift-2/protocol/CollectionType/#prop-isEmpty

[astigsen]

isEmpty() has a default implementation that just checks the count

Cool. We should make sure that is reflected in the API docs as well. ​ Does this also extend to the Realm?

[jpsim]

Cool. We should make sure that is reflected in the API docs as well.

realm/jazzy#8 (and realm/jazzy#190, kind of) would be the appropriate way to solve this I think.

Does this also extend to the Realm?

No, since Realm doesn't conform to CollectionType. We could conceivably add a Realm.isEmpty property, but can you think of practical cases in which that would be preferable to checking if the file exists, or if the count of a particular model class is empty?

[astigsen]

​> can you think of practical cases in which that would be preferable to checking if the file exists, or if the count of a particular model class is empty? Yes, I have often had need of initializing the data model with some data form the initial empty state, and while you could select a specific class to check on, it doesn't really capture the intention.

[jpsim]

Checking if it was empty also wouldn't capture the intention of having initial data (not just seeding data whenever the Realm is empty, even on subsequent runs).

For that, I'd recommend comparing the schema version with RLMNotVersioned: https://realm.io/docs/objc/latest/api/Classes/RLMRealm.html#//api/name/schemaVersionAtPath:error:

[astigsen]

I guess there are two separate issues:

One is to be able to detect if the Realm has just been created so that you can do any initial initialization you would want to do.

The other is to detect if the Realm is empty (contains no objects). There are use cases where this would be useful, like if you have lot of Realms and want to delete all the empty ones. This is currently pretty difficult to do manually as you have to find out how to iterate over all the classes in the Realm.

I think that both aught to be supported in a way that is easy for users to discover.