layoutSubviews

import Combine

func stringIfOver42(_ value: Int) -> String? {
    value > 42 ? "\(value)" : nil
}

let voidSubject = PassthroughSubject<Void, Never>()
let intSubject = PassthroughSubject<Int, Never>()

let publisher = voidSubject

layoutSubviews

import Combine
import Foundation

let c = Publishers
    .CombineLatest(
        Just(true)
            .delay(for: .seconds(0.5), scheduler: DispatchQueue(label: "A"))
            .prepend(false),
        Just(true)
            .delay(for: .seconds(1), scheduler: DispatchQueue(label: "B"))

layoutSubviews

func testCombineLatest() {
    for _ in 1...100 {
        let e = expectation(description: "Each subject should emit true")
        let s1 = CurrentValueSubject<Bool, Never>(false)
        let s2 = CurrentValueSubject<Bool, Never>(false)
        let cancellable = Publishers.CombineLatest(s1, s2)
            .sink {
                if $0, $1 {
                    e.fulfill()
                }