Meodinger

/**
 * Can assign only once
 */
class AssignOnce<T> {

    private var _backing: T? = null

    operator fun getValue(thisRef: Any, property: KProperty<*>) = _backing!!
    operator fun setValue(thisRef: Any, property: KProperty<*>, value: T) {
        synchronized(this) {

Meodinger

/**
 * Kotlin try-with-resources practice
 * All streams want to be auto-closed should run `autoClose()`
 * Simple as origin syntax!
 */
inline fun using(crossinline block: ResourceManager.() -> Unit): Catcher {
    val manager = ResourceManager()
    try {
        // Use manager's auto close
        manager.use(block)

Meodinger

/**
 * Support implicit conversion form Any? to boolean
 * Use JavaScript standard
 * Example: (_if_({ null }) { 0 } _else_ { 1 })() -> 1
 */
open class _if_<T>(private val condition: () -> Any?, private val ifBlock: () -> T) {

    companion object {
        fun Any?.logic(): Boolean {
            return when (this) {

Meodinger

/**
 * Kotlin Promise
 * Just like the Promise in JavaScript
 * Aplha Standard
 */

typealias Resolve<T>       = (T) -> Unit // T    : Any?
typealias OnResolved<T, R> = (T) -> R    // T, R : Any?
typealias Reject<U>        = (U) -> Unit // U    : Throwable
typealias OnRejected<U, V> = (U) -> V    // U, V : Throwable