Make RealmSwift write and update an Object keeping the existing relationships

UpdateRealmObject.swift

/**
 Writes a set of objects in the database.
 
 - parameter objects:         Array of `Objects` to be stored on the database
 - parameter configuration:   Realm `Configuration` in which the write action will be performed
 - parameter update:          Enabled the custom *update* maintaining existing relationships
 */
static func write(objects : [Object], configuration: Realm.Configuration, update: Bool = false) {
    if let realm = try? Realm(configuration: configuration) {
        realm.beginWrite()
        for object in objects {
            if let key = object.dynamicType.primaryKey(), value = object[key] where update {
                if let existingObject = realm.objectForPrimaryKey(object.dynamicType, key: value) {
                    let relationships = existingObject.objectSchema.properties.filter { $0.type == .Array }
                    for relationship in relationships {
                        if let newObjectRelationship = object[relationship.name] as? ListBase where newObjectRelationship.count == 0 {
                            object[relationship.name] = existingObject[relationship.name]
                        }
                    }
                }
            }
            realm.add(object, update: update)
        }
        
        do {
            try realm.commitWrite()
        }
        catch let writeError {
            debugPrint("Unable to commit write: \(writeError)")
        }
        
        realm.refresh()
    }
}

Do you manage to get List properties in existingObject.objectSchema.properties ?
I have read (sorry don't remember where) that they are stored in computedProperties that is not available in swift