Basics

0068/ComposableArchitecture.playground/Contents.swift

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+import Combine
+import SwiftUI
+
+class AppState: ObservableObject {
+  @Published var count = 0
+  @Published var favoritePrimes: [Int] = []
+  @Published var loggedInUser: User? = nil
+  @Published var activityFeed: [Activity] = []
+
+  struct Activity {
+    let timestamp: Date
+    let type: ActivityType
+
+    enum ActivityType {
+      case addedFavoritePrime(Int)
+      case removedFavoritePrime(Int)
+    }
+  }
+
+  struct User {
+    let id: Int
+    let name: String
+    let bio: String
+  }
+}
+
+struct FavoritePrimesState {
+  var favoritePrimes: [Int]
+  var activityFeed: [AppState.Activity]
+}
+
+extension AppState {
+  var favoritePrimesState: FavoritePrimesState {
+    get {
+      FavoritePrimesState(
+        favoritePrimes: self.favoritePrimes,
+        activityFeed: self.activityFeed
+      )
+    }
+    set {
+      self.favoritePrimes = newValue.favoritePrimes
+      self.activityFeed = newValue.activityFeed
+    }
+  }
+}
+
+struct PrimeAlert: Identifiable {
+  let prime: Int
+  var id: Int { self.prime }
+}
+
+struct CounterView: View {
+  @ObservedObject var state: AppState
+  @State var isPrimeModalShown = false
+  @State var alertNthPrime: PrimeAlert?
+  @State var isNthPrimeButtonDisabled = false
+
+  var body: some View {
+    VStack {
+      HStack {
+        Button("-") { self.state.count -= 1 }
+        Text("\(self.state.count)")
+        Button("+") { self.state.count += 1 }
+      }
+      Button("Is this prime?") { self.isPrimeModalShown = true }
+      Button(
+        "What is the \(ordinal(self.state.count)) prime?",
+        action: self.nthPrimeButtonAction
+      )
+      .disabled(self.isNthPrimeButtonDisabled)
+    }
+    .font(.title)
+    .navigationBarTitle("Counter demo")
+    .sheet(isPresented: self.$isPrimeModalShown) {
+      IsPrimeModalView(state: self.state)
+    }
+    .alert(item: self.$alertNthPrime) { alert in
+      Alert(
+        title: Text("The \(ordinal(self.state.count)) prime is \(alert.prime)"),
+        dismissButton: .default(Text("Ok"))
+      )
+    }
+  }
+
+  func nthPrimeButtonAction() {
+    self.isNthPrimeButtonDisabled = true
+    nthPrime(self.state.count) { prime in
+      self.alertNthPrime = prime.map(PrimeAlert.init(prime:))
+      self.isNthPrimeButtonDisabled = false
+    }
+  }
+}
+
+struct IsPrimeModalView: View {
+  @ObservedObject var state: AppState
+
+  var body: some View {
+    VStack {
+      if isPrime(self.state.count) {
+        Text("\(self.state.count) is prime 🎉")
+        if self.state.favoritePrimes.contains(self.state.count) {
+          Button("Remove from favorite primes") {
+            self.state.favoritePrimes.removeAll(where: { $0 == self.state.count })
+            self.state.activityFeed.append(.init(timestamp: Date(), type: .removedFavoritePrime(self.state.count)))
+          }
+        } else {
+          Button("Save to favorite primes") {
+            self.state.favoritePrimes.append(self.state.count)
+            self.state.activityFeed.append(.init(timestamp: Date(), type: .addedFavoritePrime(self.state.count)))
+
+          }
+        }
+      } else {
+        Text("\(self.state.count) is not prime :(")
+      }
+    }
+  }
+}
+
+struct FavoritePrimesView: View {
+  @Binding var state: FavoritePrimesState
+
+  var body: some View {
+    List {
+      ForEach(self.state.favoritePrimes, id: \.self) { prime in
+        Text("\(prime)")
+      }
+      .onDelete { indexSet in
+        for index in indexSet {
+          let prime = self.state.favoritePrimes[index]
+          self.state.favoritePrimes.remove(at: index)
+          self.state.activityFeed.append(.init(timestamp: Date(), type: .removedFavoritePrime(prime)))
+        }
+      }
+    }
+    .navigationBarTitle(Text("Favorite Primes"))
+  }
+}
+
+struct ContentView: View {
+  @ObservedObject var state: AppState
+
+  var body: some View {
+    NavigationView {
+      List {
+        NavigationLink(
+          "Counter demo",
+          destination: CounterView(state: self.state)
+        )
+        NavigationLink(
+          "Favorite primes",
+          destination: FavoritePrimesView(state: self.$state.favoritePrimesState)
+        )
+      }
+      .navigationBarTitle("State management")
+    }
+  }
+}
+
+import PlaygroundSupport
+PlaygroundPage.current.liveView = UIHostingController(
+  rootView: ContentView(state: AppState())
+)

0068/ComposableArchitecture.playground/Sources/Util.swift

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+import Foundation
+
+private let wolframAlphaApiKey = "6H69Q3-828TKQJ4EP"
+
+private struct WolframAlphaResult: Decodable {
+  let queryresult: QueryResult
+
+  struct QueryResult: Decodable {
+    let pods: [Pod]
+
+    struct Pod: Decodable {
+      let primary: Bool?
+      let subpods: [SubPod]
+
+      struct SubPod: Decodable {
+        let plaintext: String
+      }
+    }
+  }
+}
+
+private func wolframAlpha(query: String, callback: @escaping (WolframAlphaResult?) -> Void) -> Void {
+  var components = URLComponents(string: "https://api.wolframalpha.com/v2/query")!
+  components.queryItems = [
+    URLQueryItem(name: "input", value: query),
+    URLQueryItem(name: "format", value: "plaintext"),
+    URLQueryItem(name: "output", value: "JSON"),
+    URLQueryItem(name: "appid", value: wolframAlphaApiKey),
+  ]
+
+  URLSession.shared.dataTask(with: components.url(relativeTo: nil)!) { data, response, error in
+    callback(
+      data
+        .flatMap { try? JSONDecoder().decode(WolframAlphaResult.self, from: $0) }
+    )
+  }
+  .resume()
+}
+
+public func nthPrime(_ n: Int, callback: @escaping (Int?) -> Void) -> Void {
+  wolframAlpha(query: "prime \(n)") { result in
+    callback(
+      result
+        .flatMap {
+          $0.queryresult
+            .pods
+            .first(where: { $0.primary == .some(true) })?
+            .subpods
+            .first?
+            .plaintext
+      }
+      .flatMap(Int.init)
+    )
+  }
+}
+
+public func ordinal(_ n: Int) -> String {
+  let formatter = NumberFormatter()
+  formatter.numberStyle = .ordinal
+  return formatter.string(for: n) ?? ""
+}
+
+public func isPrime (_ p: Int) -> Bool {
+  if p <= 1 { return false }
+  if p <= 3 { return true }
+  for i in 2...Int(sqrtf(Float(p))) {
+    if p % i == 0 { return false }
+  }
+  return true
+}

0068/ComposableArchitecture.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>