class User: Object {

    var company: Company? = Company()
    dynamic var password = ""
    dynamic var email = ""

    func persist() {
        let realm = try! Realm()
        try! realm.write {
            realm.add(self)
        }
        print(company)
    }
}

class Company: Object {
    dynamic var id = ""
    dynamic var name = ""
}

let user = User()
user.email = "john@apple.com"
user.password = "hey"

user.company?.name = "apple"
user.company?.id = "12"

// here, if I check with debugger, all variable are properly filled
user.persist()

// here : company is = nil
// it is nil at the 'print(company)
// it is not nil before