Helpers for making stores stateless/actionless (#45)

Author: stephencelis

Examples/CaseStudies/SwiftUICaseStudies/01-GettingStarted-Animations.swift

@@ -33,27 +33,29 @@ struct AnimationsView: View {
   let store: Store<AnimationsState, AnimationsAction>
 
   var body: some View {
-    GeometryReader { proxy in
-      WithViewStore(self.store) { viewStore in
+    WithViewStore(self.store.stateless) { actionViewStore in
+      GeometryReader { proxy in
         ZStack(alignment: .center) {
           Text(template: readMe, .body)
             .padding()
 
-          Circle()
-            .fill(Color.white)
-            .blendMode(.difference)
-            .frame(width: 50, height: 50)
-            .offset(
-              x: viewStore.circleCenter.x - proxy.size.width / 2,
-              y: viewStore.circleCenter.y - proxy.size.height / 2
+          WithViewStore(self.store.scope(state: \.circleCenter)) { circleCenterViewStore in
+            Circle()
+              .fill(Color.white)
+              .blendMode(.difference)
+              .frame(width: 50, height: 50)
+              .offset(
+                x: circleCenterViewStore.x - proxy.size.width / 2,
+                y: circleCenterViewStore.y - proxy.size.height / 2
             )
+          }
         }
         .frame(maxWidth: .infinity, maxHeight: .infinity)
         .background(Color.white)
         .gesture(
           DragGesture(minimumDistance: 0).onChanged { gesture in
             withAnimation(.interactiveSpring(response: 0.25, dampingFraction: 0.1)) {
-              viewStore.send(.tapped(gesture.location))
+              actionViewStore.send(.tapped(gesture.location))
             }
           }
         )

Sources/ComposableArchitecture/Store.swift

@@ -179,6 +179,15 @@ public final class Store<State, Action> {
     }
   }
 
+  public var stateless: Store<Void, Action> {
+    self.scope(state: { _ in () })
+  }
+
+  public var actionless: Store<State, Never> {
+    func absurd<A>(_ never: Never) -> A {}
+    return self.scope(state: { $0 }, action: absurd)
+  }
+
   private init(
     initialState: State,
     reducer: @escaping (inout State, Action) -> Effect<Action, Never>

Sources/ComposableArchitecture/SwiftUI/IfLetStore.swift

@@ -1,8 +1,9 @@
 import SwiftUI
 
 /// A view that safely unwraps a store of optional state in order to show one of two views.
-/// When the underlying state is non-`nil`, the `then` closure will be performed with a `Store`
-/// that holds onto non-optional state, and otherwise the `else` closure will be performed.
+///
+/// When the underlying state is non-`nil`, the `then` closure will be performed with a `Store` that
+/// holds onto non-optional state, and otherwise the `else` closure will be performed.
 ///
 /// This is useful for deciding between two views to show depending on an optional piece of state:
 ///
@@ -59,11 +60,8 @@ where IfContent: View, ElseContent: View {
       if let state = viewStore.state {
         return
           ViewBuilder.buildEither(first: self.ifContent(self.store.scope(state: { $0 ?? state })))
-          as _ConditionalContent<IfContent, ElseContent>
       } else {
-        return
-          ViewBuilder.buildEither(second: self.elseContent())
-          as _ConditionalContent<IfContent, ElseContent>
+        return ViewBuilder.buildEither(second: self.elseContent())
       }
     }
   }

Sources/ComposableArchitecture/SwiftUI/WithViewStore.swift

@@ -76,6 +76,21 @@ extension WithViewStore where State: Equatable {
   }
 }
 
+extension WithViewStore where State == Void {
+  /// Initializes a structure that transforms a store into an observable view store in order to
+  /// compute views from equatable store state.
+  ///
+  /// - Parameters:
+  ///   - store: A store of equatable state.
+  ///   - content: A function that can generate content from a view store.
+  public init(
+    _ store: Store<State, Action>,
+    @ViewBuilder content: @escaping (ViewStore<State, Action>) -> Content
+  ) {
+    self.init(store, removeDuplicates: ==, content: content)
+  }
+}
+
 extension WithViewStore: DynamicViewContent where State: Collection, Content: DynamicViewContent {
   public typealias Data = State