Does Realm Support Computed Property in Swift

Sorting Realm results collection on computed property?

As you suspect, you cannot persist a computed property and Realm's sorted(byKeyPath:,ascending:) method only works with persisted properties. There is no way to sort a Results instance based on a computed property while keeping the auto-updating Results.

However, there is a workaround if you don't need the auto-updating nature of Results. You can use Swift's sorted method, which takes a closure as its sorting parameter, which will result in a return value of type [Conversation]:

let conversations = realm.objects(Conversation.self).sorted(by: {$0.lastUpdated < $1.lastUpdated})

Does Realm support set max record counts

No, that isn't supported directly, although it should be fairly simple to implement yourself.

On Android it would look something like this:

realm.beginTransaction();

// Delete all records more than 90 days old
realm.where(Record.class)
  .lessThan("created", calculateCutoff())
  .findAll()
  .deleteAllFromRealm();

// Create new record
Record r = realm.createObject(Record.class);
r.setCreated(new Date())
...
realm.commitTransaction();

Update Additional Field on Realm Object with ObservedRealmObject in SwiftUI

There are a lot of ways this can be accomplished; from simply updating the updated property when the 'save' button is pressed to using KVO to observe changes to the objects name property to adding a Swift 'front end' to the objects objc properties that can be handled through Computed Properties.

Let's use the third option using Swift Computed Properties and modify the Item in the question.

class Item: Object, ObjectKeyIdentifiable{
    @objc dynamic var _id = UUID().uuidString
    @objc private dynamic var _name = ""
    @objc dynamic var updated = Date()
    
    var name: String {
        get {
            return _name
        }
        set {
            _name = newValue
            updated = Date()
        }
    }
    
    convenience init(name: String) {
        self.init()
        self.name = name
    }
    
    override static func primaryKey() -> String? {
        return "_id"
    }
}

A few things to note:

The realm name property was made private with a name change to _name. I did that so you don't accidentally set it and go around the Swift implementation.

We then added a new Swift name property that acts as the 'front end' property to a Realm property backed by _name.

When an item is created using the convenience function let i = Item(name: "Item 0") or set within a write block someItem.name = "Updated name" the name computed property sets the Realm property and also populates the updated property

set {
   _name = newValue
   updated = Date()
}

This should work seamlessly with @ObservedRealmObject

Realm database callbacks

What you are looking for are computed properties. However, Realm currently doesn't support storing computed properties, but you don't really need to persist fullName in Realm, since as long as givenName and familyName are persisted, you can always compute fullName.

class Contact: Object {
    @objc dynamic var uid: String? = nil
    @objc dynamic var givenName: String? = nil
    @objc dynamic var familyName: String? = nil
    var fullName: String? {
        if let givenName = givenName, let familyName = familyName {
            return "\(givenName) \(familyName)"
        }
        return nil
    }
}

Swift Saving Structured Data to realm database

You need to persist the container too.

@Persisted var coordinates = List<TripRoute>()

The TripRoute objects are probably stored in the db somewhere but there is nothing tying them to your TripModel object.

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