Added Reducer.combine instance method (pointfreeco#85)

* Added Reducer.combine instance method * Changes name to combined(with:)
johankool · May 13, 2020 · 1e9af44 · 1e9af44
1 parent 17439d8
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diff --git a/Sources/ComposableArchitecture/Reducer.swift b/Sources/ComposableArchitecture/Reducer.swift
@@ -75,6 +75,15 @@ public struct Reducer<State, Action, Environment> {
     }
   }
 
+  /// Combines a reducer with another given reducer by running each one on the state, and
+  /// concatenating both of their effects.
+  ///
+  /// - Parameter other: Another reducer.
+  /// - Returns: A single reducer.
+  public func combined(with other: Reducer) -> Reducer {
+    Reducer.combine(self, other)
+  }
+
   /// Transforms a reducer that works on local state, action and environment into one that works on
   /// global state, action and environment. It accomplishes this by providing 3 transformations to
   /// the method:

diff --git a/Tests/ComposableArchitectureTests/ReducerTests.swift b/Tests/ComposableArchitectureTests/ReducerTests.swift
@@ -69,6 +69,42 @@ final class ReducerTests: XCTestCase {
     )
   }
 
+  func testCombine() {
+    enum Action: Equatable {
+      case increment
+    }
+
+    var childEffectExecuted = false
+    let childReducer = Reducer<Int, Action, Void> { state, _, _ in
+      state += 1
+      return Effect.fireAndForget { childEffectExecuted = true }
+        .eraseToEffect()
+    }
+
+    var mainEffectExecuted = false
+    let mainReducer = Reducer<Int, Action, Void> { state, _, _ in
+      state += 1
+      return Effect.fireAndForget { mainEffectExecuted = true }
+        .eraseToEffect()
+    }
+    .combined(with: childReducer)
+
+    let store = TestStore(
+      initialState: 0,
+      reducer: mainReducer,
+      environment: ()
+    )
+
+    store.assert(
+      .send(.increment) {
+        $0 = 2
+      }
+    )
+
+    XCTAssertTrue(childEffectExecuted)
+    XCTAssertTrue(mainEffectExecuted)
+  }
+
   func testPrint() {
     struct Unit: Equatable {}
     struct State: Equatable { var count = 0 }