CurrentValueSubject - combine

ViewController.swift

// Create a new search subject with a default value
let searchSubject = CurrentValueSubject<String, Never>("")

// Subscribe to updates
searchSubject
  .debounce(for: 0.3, scheduler: DispatchQueue.main)
  .map(searchBook(for:))
  .flatMap {$0.map(\.author)}
  .subscribe(on: DispatchQueue.main)
  .sink { author in
    print("Book author from API:", author)
  }
  .store(in: &cancellables)

print(searchSubject.value) // empty string

// Send new search i.e. search bar
searchSubject.send("th") // too short of time we debounce
DispatchQueue.main.asyncAfter(deadline: .now() + 0.4) {
  searchSubject.send("the 4 hour") // debounce
  searchSubject.send("the 4 hour work week") // search
}