RxPlayground demo

source.swift

import UIKit

import RxSwift
import RxCocoa
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

// PublishRelay vs BehaviorRelay
do {
    let relay = PublishRelay<Int>()

    relay.accept(0)
    // subscribeしてから値が流れてくる
    _ = relay.subscribe(onNext: { print("PublishRelay", $0) })

    relay.accept(1)
    relay.accept(2)
}

do {
    let relay = BehaviorRelay<Int>(value: 0)

    // subscribeした時に直近の値がすぐ流れてくる
    _ = relay.subscribe(onNext: { print("BehaviorRelay", $0) })

    relay.accept(1)
    relay.accept(2)
    // `.value` で直近の値をすぐに取り出せる
    print(relay.value)
}

// Signal vs Driver
do {
    let relay = PublishRelay<Int>()
    // PublishRelay → Signalはそのまま変換できる
    let signal = relay.asSignal()

    relay.accept(0)

    // subscribeしてから値が流れてくる
    _ = signal.emit(onNext: { print("Signal", $0) })

    relay.accept(1)
    relay.accept(2)
}

do {
    let relay = BehaviorRelay<Int>(value: 0)
    let driver = relay.asDriver()
    // subscribeした時に直近の値がすぐ流れてくる
    _ = driver.drive(onNext: { print("Driver", $0) })

    relay.accept(1)
    relay.accept(2)
}

// withLatestFrom
do {
    class View {
        let buttonDidTap = Observable.just(())
        let userID = BehaviorRelay<String>(value: "")
        let requestAPITrigger = PublishRelay<String>()
        let disposeBag = DisposeBag()

        func run() {
            buttonDidTap
                .subscribe(onNext: { [weak self] in
                    guard let self = self else { return }
                    self.requestAPITrigger.accept(self.userID.value)
                })
                .disposed(by: disposeBag)
        }

    }

    class View2 {
        let buttonDidTap = Observable.just(())
        let userID = BehaviorRelay<String>(value: "")
        let requestAPITrigger = PublishRelay<String>()
        let disposeBag = DisposeBag()

        func run() {
            buttonDidTap
                .withLatestFrom(userID)
                .bind(to: requestAPITrigger)
                .disposed(by: disposeBag)
        }
    }

}

// zip
do {
    let relay = PublishRelay<Int>()

    _ = Observable
        .zip(relay, relay.skip(1))
        .subscribe(onNext: { print("Before: \($0.0), After: \($0.1)")})

    relay.accept(1)
    relay.accept(1)
    relay.accept(2)
    relay.accept(3)
    relay.accept(5)
    relay.accept(8)
}

// scan, startWith
do {
    let disposeBag = DisposeBag()
    let numbers = PublishRelay<[Int]>()


    let relay = PublishRelay<[Int]>()

    relay
        .scan([], accumulator: { $0.isEmpty ? $1 : $0 + $1 })
        .startWith([])
        .bind(to: numbers)
        .disposed(by: disposeBag)

    _ = numbers.subscribe(onNext: { print("numbers", $0)})

    relay.accept([1, 2, 3])
    relay.accept([4, 5, 6])
}