(Do not merge!) Discussion: A userland replacement for replaceReducer

examples/counter/index.js

@@ -1,7 +1,13 @@
 import React from 'react';
-import Root from './containers/Root';
+import { Provider } from 'react-redux';
+import CounterApp from './containers/CounterApp';
+import configureStore from './store/configureStore';
+
+const store = configureStore();
 
 React.render(
-  <Root />,
+  <Provider store={store}>
+    {() => <CounterApp />}
+  </Provider>,
   document.getElementById('root')
-);
+)

examples/counter/store/configureStore.js

@@ -1,11 +1,21 @@
-import { createStore, applyMiddleware } from 'redux';
+import { createStore, applyMiddleware, compose } from 'redux';
 import thunk from 'redux-thunk';
-import rootReducer from '../reducers';
+import reducer from '../reducers';
+import switchReducer from './switchReducer';
 
-const createStoreWithMiddleware = applyMiddleware(
-  thunk
-)(createStore);
+function onHotReload(useReducer) {
+  module.hot.accept('../reducers', () => {
+    const nextReducer = require('../reducers');
+    useReducer(nextReducer);
+  });
+}
+
+const finalCreateStore = compose(
+  switchReducer(onHotReload),
+  applyMiddleware(thunk),
+  createStore
+);
 
 export default function configureStore(initialState) {
-  return createStoreWithMiddleware(rootReducer, initialState);
+  return finalCreateStore(reducer, initialState);
 }

examples/counter/store/switchReducer.js

@@ -0,0 +1,19 @@
+// Note: this is meant to be provided in a separate package.
+// I'm only including it here for discussion.
+
+const SWITCH_REDUCER = { type: 'redux-switch/SWITCH_REDUCER' };
+
+export default function switchReducer(onNextReducer) {
+  return next => (reducer, initialState) => {
+    let currentReducer = reducer;
+    let switchingReducer = (state, action) => currentReducer(state, action);
+    let store = next(switchingReducer, initialState);
+
+    onNextReducer(nextReducer => {
+      currentReducer = nextReducer;
+      store.dispatch({ type: SWITCH_REDUCER });
+    });
+
+    return store;
+  };
+}