It makes more sense now

src/components/Post.js

@@ -5,23 +5,37 @@ import { fetchPost } from '../actions';
 import { Link } from 'react-router-dom';
 
 class Post extends React.Component {
+    constructor (props) {
+        super(props)
+        this.state = {
+            isLoading: true
+        }
+    }
     componentDidMount() {
         const { slug } = this.props.match.params
-        this.props.fetchPost(slug);
+        this.props.fetchPost(slug)
+            .then(() => this.setState({isLoading: false}))
     }
 
     render () {
-        console.log(this.props.posts)
-        return (
-            <div className="item" key="{post.id}">
-                <div className="content">
-                    <div className="description">
-                        <h1><b><u><Link to={"/posts/"}>""</Link></u></b></h1>
-                        <ReactMarkdown source="{post.content}" />
+        const {posts} = this.props
+        const {isLoading} = this.state
+
+        if (isLoading) {
+            return <p>Loading</p>
+        } else {
+            const post = posts.entities[posts.currentId]
+            return (
+                <div className="item" key={post.id}>
+                    <div className="content">
+                        <div className="description">
+                            <h1><b><u><Link to={"/posts/" + post.slug}>{post.title}</Link></u></b></h1>
+                            <ReactMarkdown source={post.content} />
+                        </div>
                     </div>
                 </div>
-            </div>
-        );
+            );
+        }
     }
 }
 

src/reducers/postsReducer.js

@@ -1,5 +1,6 @@
 const initialState = {
     entities: {},
+    currentId: ""
 };
 
 const normalizeEntities = (entities, payloadData) => {
@@ -9,12 +10,15 @@ const normalizeEntities = (entities, payloadData) => {
 }
 
 export default (state = initialState, action) => {
+    let mergedEntities = {}
     switch (action.type) {
         case 'FETCH_POSTS':
-            const mergedEntities = normalizeEntities(state.entities, action.payload)
+            mergedEntities = normalizeEntities(state.entities, action.payload)
             return {...state, ...{entities: mergedEntities}}
+
         case 'FETCH_POST':
-            return action.payload;
+            mergedEntities = normalizeEntities(state.entities, [action.payload])
+            return {...state, ...{entities: mergedEntities, currentId: action.payload.id}}
         default:
             return state;
     }