How to link two Realm objects

I'm new to iOS development and currently using Realm as database. My first tableview display Restaurant object and second table display customer objects. How can i link this two objects?. Means when i click each restaurant it will display different customer.

class Restaurant: Object {
    dynamic var restname: String = ""
    dynamic var date: String = ""
}

class Customer: Object {
    dynamic var id = 0
    dynamic var name: String = ""
    dynamic var price: Float = 0.0
    dynamic var drinks: Float = 0.0

    override static func primaryKey() -> String? {
        return "id"
    }
}