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()
    }
}

Thanks you ! :)
Here is a update for Swift 3

    /**
     Writes a set of objects in the database.

     - parameter entityList:         Array of `Objects` to be stored on the database
     - parameter update:          Enabled the custom *update* maintaining existing relationships
     */
    func save(entityList: [Object], shouldUpdate update: Bool = false) {
        database.beginWrite()
        for entity in entityList {
            if let key = type(of: entity).primaryKey(), let value = entity[key] , update {
                if let existingObject = self.database.object(ofType: type(of: entity), forPrimaryKey: value as AnyObject) {
                    let relationships = existingObject.objectSchema.properties.filter {
                        $0.type == .array
                    }
                    for relationship in relationships {
                        if let newObjectRelationship = entity[relationship.name] as? ListBase , newObjectRelationship.count == 0 {
                            entity[relationship.name] = existingObject[relationship.name]
                        }
                    }
                }
            }
            database.add(entity, update: update)
        }

        do {
            try database.commitWrite()
        } catch let writeError {
            debugPrint("Unable to commit write: \(writeError)")
        }

        database.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