Merge pull request #9 from dphilipson/feature/case-with-action

Feature/case with action

Author: dphilipson

README.md

@@ -77,6 +77,22 @@ const reducer = reducerWithInitialState(INITIAL_STATE)
 Everything is typesafe. If the types of the action payload and handler don't line up, then
 TypeScript will complain.
 
+If the full action is needed rather than just the payload, `.caseWithAction()` may be used in
+place of `.case()`. For example:
+``` javascript
+import { Action } from "typescript-fsa";
+
+const setText = actionCreator<string>("SET_TEXT");
+
+const reducer = reducerWithInitialState({ text, lastEditBy: "" })
+    .caseWithAction(incrementCount, (state, { payload, meta }) => ({
+        text: payload,
+        lastEditBy: meta.author,
+    }));
+
+// Returns { text: "hello", lastEditBy: "cbrontë" }.
+reducer(undefined, setText("hello", { author: "cbrontë" }));
+```
 The reducer builder chains are mutable. Each call to `.case()` modifies the callee to respond to the
 specified action type. If this is undesirable, see the [`.build()`](#build) method below.
 
@@ -169,11 +185,17 @@ function reducer(state: State, action: Redux.Action): State {
 
 ### Reducer chain methods
 
-#### `.case(actionCreator, handler)`
+#### `.case(actionCreator, handler(state, payload) => newState)`
 
 Mutates the reducer such that it applies `handler` when passed actions matching the type of
 `actionCreator`. For examples, see [Usage](#usage).
 
+#### `.caseWithAction(actionCreator, handler(state, action) => newState)`
+
+Like `.case()`, except that `handler` receives the entire action as its second argument rather
+than just the payload. This is useful if you want to read other properties of the action, such as
+`meta` or `error`. For an example, see [Usage](#usage).
+
 #### `.build()`
 
 Returns a plain reducer function whose behavior matches the current state of the reducer chain.

__tests__/test.ts

@@ -66,6 +66,19 @@ describe("reducer builder", () => {
         expect(reducer(initialState, dataToUpperCase)).toEqual({ data: "HELLO" });
     });
 
+    it("should call full-action handler when using .caseWithAction()", () => {
+        const reducer = reducerWithInitialState(initialState)
+            .caseWithAction(sliceData, (state, action) => ({
+                ...state,
+                data: state.data.slice(action.payload),
+                meta: { author: "cbrontë" },
+            }));
+        expect(reducer(undefined, sliceData(1, "meta"))).toEqual({
+            data: "ello",
+            meta: { author: "cbrontë" },
+        });
+    });
+
     it("should call upcasting handler on matching action", () => {
         const reducer = upcastingReducer<StateWithCount, State>()
             .case(toBasicState, toBasicStateHandler);

src/index.ts

@@ -1,7 +1,11 @@
-import { ActionCreator, AnyAction, isType } from "typescript-fsa";
+import { Action, ActionCreator, AnyAction, isType } from "typescript-fsa";
 
 export interface ReducerBuilder<InS extends OutS, OutS> {
     case<P>(actionCreator: ActionCreator<P>, handler: Handler<InS, OutS, P>): ReducerBuilder<InS, OutS>;
+    caseWithAction<P>(
+        actionCreator: ActionCreator<P>,
+        handler: Handler<InS, OutS, Action<P>>,
+    ): ReducerBuilder<InS, OutS>;
     build(): (state: InS, action: AnyAction) => OutS;
     (state: InS, action: AnyAction): OutS;
 }
@@ -24,7 +28,7 @@ export function upcastingReducer<InS extends OutS, OutS>(): ReducerBuilder<InS,
 
 interface Case<InS extends OutS, OutS, P> {
     actionCreator: ActionCreator<P>;
-    handler: Handler<InS, OutS, P>;
+    handler: Handler<InS, OutS, Action<P>>;
 }
 
 type CaseList<InS extends OutS, OutS> = Array<Case<InS, OutS, any>>;
@@ -33,14 +37,17 @@ function makeReducer<InS extends OutS, OutS>(initialState?: InS): ReducerBuilder
     const cases: CaseList<InS, OutS> = [];
     const reducer = getReducerFunction(initialState, cases) as ReducerBuilder<InS, OutS>;
 
-    reducer.case = <P>(
+    reducer.caseWithAction = <P>(
         actionCreator: ActionCreator<P>,
-        handler: Handler<InS, OutS, P>
-    ): ReducerBuilder<InS, OutS> => {
+        handler: Handler<InS, OutS, Action<P>>,
+    ) => {
         cases.push({ actionCreator, handler });
         return reducer;
     };
 
+    reducer.case = <P>(actionCreator: ActionCreator<P>, handler: Handler<InS, OutS, P>) =>
+        reducer.caseWithAction(actionCreator, (state, action) => handler(state, action.payload));
+
     reducer.build = () => getReducerFunction(initialState, cases.slice());
 
     return reducer;
@@ -54,7 +61,7 @@ function getReducerFunction<InS extends OutS, OutS>(
         for (let i = 0, length = cases.length; i < length; i++) {
             const { actionCreator, handler } = cases[i];
             if (isType(action, actionCreator)) {
-                return handler(state, action.payload);
+                return handler(state, action);
             }
         }
         return state;