part 10

src/index.js

@@ -10,7 +10,7 @@ function render() {
   ReactDOM.render(
     <App
       stories={store.storyStore.readableStories}
-      onArchive={(objectID) => store.archiveStore.archivedStoryIds.push(objectID)}
+      onArchive={(objectID) => store.archiveStore.archiveStory(objectID)}
     />,
     document.getElementById('root')
   );

src/stores/archiveStore.js

@@ -1,11 +1,14 @@
-import { observable } from 'mobx';
+import { observable, action } from 'mobx';
 
 class ArchiveStore {
   @observable archivedStoryIds = [];
 
   constructor(rootStore) {
     this.rootStore = rootStore;
   }
+
+  @action archiveStory = id =>
+    this.archivedStoryIds.push(id);
 }
 
 export default ArchiveStore;

src/stores/index.js

@@ -1,6 +1,10 @@
+import { useStrict } from 'mobx';
+
 import StoryStore from './storyStore';
 import ArchiveStore from './archiveStore';
 
+useStrict(true);
+
 class RootStore {
   constructor() {
     this.storyStore = new StoryStore(this);