Simplify effects basics case study. (#1166)

* Simplify effects basics case study.

* wip

* Update Examples/CaseStudies/SwiftUICaseStudies/02-Effects-Basics.swift

Co-authored-by: Stephen Celis <[email protected]>

* nb

Co-authored-by: Stephen Celis <[email protected]>

Author: mluisbrown

Examples/CaseStudies/SwiftUICaseStudies/02-Effects-Basics.swift

@@ -15,13 +15,9 @@ private let readMe = """
   file access, socket connections, and anytime a scheduler is involved (such as debouncing, \
   throttling and delaying), and they are typically difficult to test.
 
-  This application has two simple side effects:
-
-  • Each time you count down the number will be incremented back up after a delay of 1 second.
-  • Tapping "Number fact" will trigger an API request to load a piece of trivia about that number.
-
-  Both effects are handled by the reducer, and a full test suite is written to confirm that the \
-  effects behave in the way we expect.
+  This application has a simple side effect: tapping "Number fact" will trigger an API request to \
+  load a piece of trivia about that number. This effect is handled by the reducer, and a full test \
+  suite is written to confirm that the effect behaves in the way we expect.
   """
 
 // MARK: - Feature domain
@@ -47,15 +43,15 @@ struct EffectsBasicsEnvironment {
 // MARK: - Feature business logic
 
 let effectsBasicsReducer = Reducer<
-  EffectsBasicsState, EffectsBasicsAction, EffectsBasicsEnvironment
+  EffectsBasicsState,
+  EffectsBasicsAction,
+  EffectsBasicsEnvironment
 > { state, action, environment in
   switch action {
   case .decrementButtonTapped:
     state.count -= 1
     state.numberFact = nil
-    // Return an effect that re-increments the count after 1 second.
-    return Effect(value: EffectsBasicsAction.incrementButtonTapped)
-      .delay(1, on: environment.mainQueue)
+    return .none
 
   case .incrementButtonTapped:
     state.count += 1
@@ -77,6 +73,7 @@ let effectsBasicsReducer = Reducer<
     return .none
 
   case .numberFactResponse(.failure):
+    // NB: This is where we could handle the error is some way, such as showing an alert.
     state.isNumberFactRequestInFlight = false
     return .none
   }
@@ -90,15 +87,11 @@ struct EffectsBasicsView: View {
   var body: some View {
     WithViewStore(self.store) { viewStore in
       Form {
-        Section(header: Text(readMe)) {
-          EmptyView()
+        Section {
+          Text(readMe)
         }
 
-        Section(
-          footer: Button("Number facts provided by numbersapi.com") {
-            UIApplication.shared.open(URL(string: "http://numbersapi.com")!)
-          }
-        ) {
+        Section {
           HStack {
             Spacer()
             Button("−") { viewStore.send(.decrementButtonTapped) }
@@ -110,15 +103,29 @@ struct EffectsBasicsView: View {
           .buttonStyle(.borderless)
 
           Button("Number fact") { viewStore.send(.numberFactButtonTapped) }
+            .frame(maxWidth: .infinity)
+
           if viewStore.isNumberFactRequestInFlight {
             ProgressView()
+              .frame(maxWidth: .infinity)
+              // NB: There seems to be a bug in SwiftUI where the progress view does not show
+              // a second time unless it is given a new identity.
+              .id(UUID())
           }
 
           if let numberFact = viewStore.numberFact {
             Text(numberFact)
           }
         }
+
+        Section {
+          Button("Number facts provided by numbersapi.com") {
+            UIApplication.shared.open(URL(string: "http://numbersapi.com")!)
+          }
+          .foregroundColor(.gray)
+        }
       }
+      .buttonStyle(.borderless)
     }
     .navigationBarTitle("Effects")
   }

Examples/CaseStudies/SwiftUICaseStudies/02-Effects-Cancellation.swift

@@ -81,12 +81,11 @@ struct EffectsCancellationView: View {
   var body: some View {
     WithViewStore(self.store) { viewStore in
       Form {
-        Section(
-          header: Text(readMe),
-          footer: Button("Number facts provided by numbersapi.com") {
-            UIApplication.shared.open(URL(string: "http://numbersapi.com")!)
-          }
-        ) {
+        Section {
+          Text(readMe)
+        }
+
+        Section {
           Stepper(
             value: viewStore.binding(
               get: \.count, send: EffectsCancellationAction.stepperChanged)
@@ -99,6 +98,9 @@ struct EffectsCancellationView: View {
               Button("Cancel") { viewStore.send(.cancelButtonTapped) }
               Spacer()
               ProgressView()
+                // NB: There seems to be a bug in SwiftUI where the progress view does not show
+                // a second time unless it is given a new identity.
+                .id(UUID())
             }
           } else {
             Button("Number fact") { viewStore.send(.triviaButtonTapped) }
@@ -109,7 +111,15 @@ struct EffectsCancellationView: View {
             Text($0).padding(.vertical, 8)
           }
         }
+
+        Section {
+          Button("Number facts provided by numbersapi.com") {
+            UIApplication.shared.open(URL(string: "http://numbersapi.com")!)
+          }
+          .foregroundColor(.gray)
+        }
       }
+      .buttonStyle(.borderless)
     }
     .navigationBarTitle("Effect cancellation")
   }

Examples/CaseStudies/SwiftUICaseStudies/FactClient.swift

@@ -17,12 +17,12 @@ extension FactClient {
     static let live = Self(
       fetch: { number in
         Effect.task {
+          try? await Task.sleep(nanoseconds: NSEC_PER_SEC)
           do {
             let (data, _) = try await URLSession.shared
               .data(from: URL(string: "http://numbersapi.com/\(number)/trivia")!)
             return String(decoding: data, as: UTF8.self)
           } catch {
-            try? await Task.sleep(nanoseconds: NSEC_PER_SEC)
             return "\(number) is a good number Brent"
           }
         }
@@ -51,10 +51,7 @@ extension FactClient {
     // This is the "failing" fact dependency that is useful to plug into tests that you want
     // to prove do not need the dependency.
     static let failing = Self(
-      fetch: { _ in
-        XCTFail("\(Self.self).fact is unimplemented.")
-        return .none
-      }
+      fetch: { _ in .failing("\(Self.self).fact is unimplemented.") }
     )
   }
 #endif

Examples/CaseStudies/SwiftUICaseStudiesTests/02-Effects-BasicsTests.swift

@@ -5,7 +5,7 @@ import XCTest
 @testable import SwiftUICaseStudies
 
 class EffectsBasicsTests: XCTestCase {
-  func testCountDown() {
+  func testCountUpAndDown() {
     let store = TestStore(
       initialState: EffectsBasicsState(),
       reducer: effectsBasicsReducer,
@@ -21,21 +21,18 @@ class EffectsBasicsTests: XCTestCase {
     store.send(.decrementButtonTapped) {
       $0.count = 0
     }
-    store.receive(.incrementButtonTapped) {
-      $0.count = 1
-    }
   }
 
-  func testNumberFact() {
+  func testNumberFact_HappyPath() {
     let store = TestStore(
       initialState: EffectsBasicsState(),
       reducer: effectsBasicsReducer,
-      environment: EffectsBasicsEnvironment(
-        fact: FactClient(fetch: { n in Effect(value: "\(n) is a good number Brent") }),
-        mainQueue: ImmediateScheduler()
-      )
+      environment: .failing
     )
 
+    store.environment.fact.fetch = { Effect(value: "\($0) is a good number Brent") }
+    store.environment.mainQueue = .immediate
+
     store.send(.incrementButtonTapped) {
       $0.count = 1
     }
@@ -47,4 +44,32 @@ class EffectsBasicsTests: XCTestCase {
       $0.numberFact = "1 is a good number Brent"
     }
   }
+
+  func testNumberFact_UnhappyPath() {
+    let store = TestStore(
+      initialState: EffectsBasicsState(),
+      reducer: effectsBasicsReducer,
+      environment: .failing
+    )
+
+    store.environment.fact.fetch = { _ in Effect(error: FactClient.Error()) }
+    store.environment.mainQueue = .immediate
+
+    store.send(.incrementButtonTapped) {
+      $0.count = 1
+    }
+    store.send(.numberFactButtonTapped) {
+      $0.isNumberFactRequestInFlight = true
+    }
+    store.receive(.numberFactResponse(.failure(FactClient.Error()))) {
+      $0.isNumberFactRequestInFlight = false
+    }
+  }
+}
+
+extension EffectsBasicsEnvironment {
+  static let failing = Self(
+    fact: .failing,
+    mainQueue: .failing
+  )
 }