Improve typing of StoreEnhancer

sergioadorna · Apr 5, 2016 · 324849d · 324849d
1 parent 3388903
commit 324849d
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Showing 2 changed files with 12 additions and 9 deletions.
diff --git a/index.d.ts b/index.d.ts
@@ -194,9 +194,8 @@ export interface Store<S> {
  * @template S State object type.
  */
 export interface StoreCreator {
-  <S>(reducer: Reducer<S>, enhancer?: StoreEnhancer): Store<S>;
-  <S>(reducer: Reducer<S>, initialState: S,
-      enhancer?: StoreEnhancer): Store<S>;
+  <S>(reducer: Reducer<S>, enhancer?: StoreEnhancer<S>): Store<S>;
+  <S>(reducer: Reducer<S>, initialState: S, enhancer?: StoreEnhancer<S>): Store<S>;
 }
 
 /**
@@ -217,7 +216,9 @@ export interface StoreCreator {
  * without the app being aware it is happening. Amusingly, the Redux
  * middleware implementation is itself a store enhancer.
  */
-export type StoreEnhancer = (next: StoreCreator) => StoreCreator;
+export type StoreEnhancer<S> = (next: StoreEnhancerStoreCreator<S>) => StoreEnhancerStoreCreator<S>;
+export type GenericStoreEnhancer = <S>(next: StoreEnhancerStoreCreator<S>) => StoreEnhancerStoreCreator<S>;
+export type StoreEnhancerStoreCreator<S> = (reducer: Reducer<S>, initialState: S) => Store<S>;
 
 /**
  * Creates a Redux store that holds the state tree.
@@ -287,7 +288,7 @@ export interface Middleware {
  * @param middlewares The middleware chain to be applied.
  * @returns A store enhancer applying the middleware.
  */
-export function applyMiddleware(...middlewares: Middleware[]): StoreEnhancer;
+export function applyMiddleware(...middlewares: Middleware[]): GenericStoreEnhancer;
 
 
 /* action creators */

diff --git a/test/typescript/store.ts b/test/typescript/store.ts
@@ -1,5 +1,5 @@
 import {
-  Store, createStore, Reducer, Action, StoreEnhancer,
+  Store, createStore, Reducer, Action, StoreEnhancer, GenericStoreEnhancer,
   StoreCreator, Unsubscribe
 } from "../../index.d.ts";
 
@@ -21,13 +21,15 @@ const storeWithInitialState: Store<State> = createStore(reducer, {
   todos: []
 });
 
-const enhancer: StoreEnhancer = (next: StoreCreator) => next;
+const genericEnhancer: GenericStoreEnhancer = next => next;
+const specificEnhencer: StoreEnhancer<State> = next => next;
 
-const storeWithEnhancer: Store<State> = createStore(reducer, enhancer);
+const storeWithGenericEnhancer: Store<State> = createStore(reducer, genericEnhancer);
+const storeWithSpecificEnhancer: Store<State> = createStore(reducer, specificEnhencer);
 
 const storeWithInitialStateAndEnhancer: Store<State> = createStore(reducer, {
   todos: []
-}, enhancer);
+}, genericEnhancer);
 
 
 /* dispatch */