gahfy

class InitialState: State{
    override fun parseCharacter(context: StateContext, character: Char){
        when{
            character == '+' || character == '-' -> {
                context.setState(SignState())
            }
            character == '0' -> {
                context.setState(ZeroState())
            }
            character in ('1'..'9') -> {

gahfy

interface State{
    fun parseCharacter(context: StateContext, character: Char)
    val final: Boolean
}

class StateContext {
    private var state: State? = null

    fun setState(state: State?){
        this.state = state

gahfy

fun main(){
    var counter = 0
    val checkbox = CheckBox()
    val printObserver = CheckboxObserver{ println("Checkbox have been clicked") }
    var countObserver = CheckboxObserver{ counter++ }
    // Nothing happens
    checkbox.click()
    checkbox.click()
    checkbox.click()
    checkbox.addObserver(countObserver)

gahfy

class CheckBox(){
    var isChecked: Boolean = false
    private val observers = mutableListOf<CheckboxObserver>()

    fun addObserver(observer: CheckboxObserver){
        observers.add(observer)
    }

    fun removeObserver(observer: CheckboxObserver){
        observers.remove(observer)

gahfy

fun interface CheckboxObserver{
    fun notifyClick()
}

gahfy

class CheckBox(){
    var isChecked: Boolean = false

    fun click(){
        isChecked = !isChecked
    }
}

fun main(){
    val checkbox = CheckBox()

gahfy

fun main(){
    val frenchCheckBox = CheckBox()
    val frenchTextView = TextView("Are you french?")

    val mediator = FormMediator(frenchCheckBox, frenchTextView)
    println("isChecked:${frenchCheckBox.isChecked} / text:${frenchTextView.getText()}")
    frenchCheckBox.click()
    println("isChecked:${frenchCheckBox.isChecked} / text:${frenchTextView.getText()}")
    frenchTextView.click()
    println("isChecked:${frenchCheckBox.isChecked} / text:${frenchTextView.getText()}")

gahfy

class FormMediator(
    private val checkbox: CheckBox,
    private val textview: TextView
): Mediator{
    init{
        checkbox.setMediator(this)
        textview.setMediator(this)
    }

    override fun notifyCheckboxClicked(){

gahfy

class CheckBox(){
    var isChecked: Boolean = false
    private var mediator: Mediator? = null

    fun click(){
        isChecked = !isChecked
        mediator?.notifyCheckboxClicked()
    }

    fun setMediator(mediator: Mediator){

gahfy

interface Mediator{
    fun notifyCheckboxClicked()
    fun notifyTextViewClicked()
}