Reactive Programming in iOS with Combine

Feb 4 2021 · Swift 5.3, macOS 11.0, Xcode 12.2

Part 2: Transforming & Filtering Operators

10. Filtering Operators

Episode complete

Play next episode

Next
About this episode

Leave a rating/review

See forum comments
Cinema mode Mark complete Download course materials
Previous episode: 09. Challenge: Create a Phone Number Lookup Next episode: 11. More Filtering Operators

Get immediate access to this and 4,000+ other videos and books.

Take your career further with a Kodeco Personal Plan. With unlimited access to over 40+ books and 4,000+ professional videos in a single subscription, it's simply the best investment you can make in your development career.

Learn more Already a subscriber? Sign in.

Heads up... You’re accessing parts of this content for free, with some sections shown as obfuscated text.

Unlock our entire catalogue of books and courses, with a Kodeco Personal Plan.

Unlock now

Heads up... You’re accessing parts of this content for free, with some sections shown as obfuscated text.

Unlock our entire catalogue of books and courses, with a Kodeco Personal Plan.

Unlock now

Filtering opertors consume values from a publisher, and conditionally decide whether to pass them onto the consumer. There are quite a few filtering operators to talk about, and even variations on those operators, so I’ve already run my own filtering operator to narrow them down to a set to go over here. Let’s get started with some filtering basics.

example(of: "filter") {
  // 1
  let numbers = (1...10).publisher

  // 2
  numbers
    .filter { $0.isMultiple(of: 3) }
    .sink(receiveValue: { n in
      print("\(n) is a multiple of 3!")
    })
    .store(in: &subscriptions)
}

example(of: "removeDuplicates") {
  // 1
  let words = "hey hey there! want to listen to mister mister ?"
                  .components(separatedBy: " ")
                  .publisher
  // 2
  words
    .removeDuplicates()
    .sink(receiveValue: { print($0) })
    .store(in: &subscriptions)
}

example(of: "compactMap") {
  // 1
  let strings = ["a", "1.24", "3",
                 "def", "45", "0.23"].publisher

  // 2
  strings
    .compactMap { Float($0) }
    .sink(receiveValue: {
      // 3
      print($0)
    })
    .store(in: &subscriptions)
}

example(of: "ignoreOutput") {
  // 1
  let numbers = (1...10_000).publisher

  // 2
  numbers
    .ignoreOutput()
    .sink(receiveCompletion: { print("Completed with: \($0)") },
          receiveValue: { print($0) })
    .store(in: &subscriptions)
}