added initial state

blog/src/reducers/index.js

@@ -1,7 +1,8 @@
 import { combineReducers } from 'redux';
+import PostsReducer from './reducer_posts';
 
 const rootReducer = combineReducers({
-  state: (state = {}) => state
+  posts: PostsReducer
 });
 
 export default rootReducer;

blog/src/reducers/reducer_posts.js

@@ -0,0 +1,12 @@
+import { FETCH_POSTS } from '../actions/index';
+
+const INITIAL_STATE = { all: [], post: null };
+
+export default function(state = INITIAL_STATE, action) {
+  switch(action.type) {
+  case FETCH_POSTS:
+
+  default:
+    return state;
+  }
+}