realtime updates

yyx990803 · yyx990803 · commit 8db2ee925fa3 · 2016-08-09T19:47:28.000-04:00
diff --git a/src/components/NewsList.vue b/src/components/NewsList.vue
@@ -27,6 +27,7 @@
 <script>
 import Spinner from './Spinner.vue'
 import NewsItem from './NewsItem.vue'
+import { watchList } from '../store/api'
 
 export default {
   name: 'NewsList',
@@ -46,7 +47,9 @@ export default {
       loading: false,
       transition: 'slide-left',
       // if this is the initial render, directly render with the store state
-      // otherwise this is a page switch, start with blank and wait for data load
+      // otherwise this is a page switch, start with blank and wait for data load.
+      // we need these local state so that we can precisely control the timing
+      // of the transitions.
       displayedPage: isInitialRender ? Number(this.$store.state.route.params.page) || 1 : -1,
       displayedItems: isInitialRender ? this.$store.getters.activeItems : []
     }
@@ -69,6 +72,16 @@ export default {
     if (this.$root._isMounted) {
       this.loadItems(this.page)
     }
+    this.unwatchList = watchList(this.type, ids => {
+      this.$store.commit('SET_LIST', { type: this.type, ids })
+      this.$store.dispatch('FETCH_ACTIVE_ITEMS').then(() => {
+        this.displayedItems = this.$store.getters.activeItems
+      })
+    })
+  },
+
+  destroyed () {
+    this.unwatchList()
   },
 
   watch: {
diff --git a/src/store/api.js b/src/store/api.js
@@ -71,3 +71,19 @@ export function fetchItem (id, forceRefresh) {
 export function fetchItems (ids) {
   return Promise.all(ids.map(id => fetchItem(id)))
 }
+
+export function watchList (type, cb) {
+  let first = true
+  const ref = api.child(`${type}stories`)
+  const handler = snapshot => {
+    if (first) {
+      first = false
+    } else {
+      cb(snapshot.val())
+    }
+  }
+  ref.on('value', handler)
+  return () => {
+    ref.off('value', handler)
+  }
+}
diff --git a/src/store/index.js b/src/store/index.js
@@ -26,8 +26,16 @@ const store = new Vuex.Store({
       commit('SET_ACTIVE_TYPE', { type })
       return fetchIdsByType(type)
         .then(ids => commit('SET_LIST', { type, ids }))
-        .then(() => fetchItems(getters.activeIds.filter(id => !state.items[id])))
-        .then(items => commit('SET_ITEMS', { items }))
+        .then(() => dispatch('FETCH_ACTIVE_ITEMS'))
+    },
+
+    FETCH_ACTIVE_ITEMS: ({ commit, state, getters }) => {
+      const ids = getters.activeIds.filter(id => !state.items[id])
+      if (ids.length) {
+        return fetchItems(ids).then(items => commit('SET_ITEMS', { items }))
+      } else {
+        return Promise.resolve()
+      }
     }
   },
 
