Something like this? ``` val isRead = AtomicBoolean(false) val testObservable = Maybe.fromCallable {...

# rx

[arekolek]

Something like this?

val isRead = AtomicBoolean(false)
val testObservable = Maybe.fromCallable { true.takeUnless { isRead.getAndSet(true) } }.toObservable()

[filipradon]

My colleage finally come up with such solution which is basically quite similar but encapsulating this flag inside a class

class ColdObservableSingleSubscriberProxy<T>(val value: T) {
    private var hasBeenSubscribed = false

    fun getObservable(): Observable<T> =
        if (hasBeenSubscribed) {
            Observable.never<T>()
        } else {
            hasBeenSubscribed = true
            Observable.just(value)
        }
}

[arekolek]

One problem with it is that the if is evaluated at assembly, not at subscription. So if you call getObservable() once, all its subscribers will still get the value

[arekolek]

image.png

[reline]

how’s this?

fun <T> Observable<T>.toColdSingleSubscribeable(): Observable<T> {
    return ColdObservableSingleSubscriberProxy(this)
}

class ColdObservableSingleSubscriberProxy<T>(private val observable: Observable<T>) : Observable<T>() {

    private val hasBeenSubscribed = AtomicBoolean(false)

    override fun subscribeActual(observer: Observer<in T>) {
        if (hasBeenSubscribed.compareAndSet(false, true)) {
            observable.subscribe(observer)
        } else {
            never<T>().subscribe(observer)
        }
    }

}

[reline]

this would always return false for isDisposed however, so use empty() instead of never() if you want it isDisposed to return true immediately after subscribing.