armancodv

let displayName = firstName ?? 'Default Name'

// it is equivalent to
let displayName = firstName !== undefined && firstName !== null ? firsName : 'Default Name' 

armancodv

console.log(car?.owner?.account?.firstName)

// it is equivalent to

console.log(
  (
    car !== undefined && car !== null &&
    car.owner !== undefined && car.owner !== null &&
    car.owner.account !== undefined && car.owner.account !== null
  ) ? car.owner.account.firstName : undefined

armancodv

console.log(user2 !== undefined && user2 !== null ? user2.firstname : undefined);

armancodv

console.log(user2?.firstname);

armancodv

const user2 = undefined;

// first approach
if(user2 !== undefined && user2 !== null) {
    console.log(user2.firstname);
}

// second approach
console.log(user2 !== undefined && user2 !== null ? user2.firstname : undefined);

armancodv

const user = {
  firstName: 'Lorem',
  lastName: 'Ipsum'
};
const user2 = undefined;

console.log(user.firstName);
// it logs 'Lorem'

console.log(user2.firstName);

armancodv

class LoginPresenter : BasePresenter<LoginContract.View>(), LoginContract.Presenter {

    override fun onViewCreated() {
        super.onViewCreated()
    }

    override fun login(email: String?, password: String?) {
    }

    override fun checkEmail(email: String) {

armancodv

abstract class BasePresenter<V : BaseContract.View> : BaseContract.Presenter<V> {
    protected var view: V? = null

    override fun onAttach(view: V) {
        this.view = view
    }

    override fun onViewCreated() {
    }

armancodv

class LoginFragment : Fragment(), LoginContract.View {
  
    private val presenter: LoginPresenter = LoginPresenter()

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_login, container, false)

armancodv

interface LoginContract {
    interface View : BaseContract.View {
        fun showEmailError(error: String?)
        fun showPasswordError(error: String?)
        fun disableButton()
        fun enableButton()
    }

    interface Presenter : BaseContract.Presenter<View> {
        fun login(email: String?, password: String?)