ensure $route is available in data() (fix #177)

Author: yyx990803

src/mixin.js

@@ -2,28 +2,45 @@ export default function (Vue) {
 
   const _ = Vue.util
   const mixin = {
-    created: function () {
-      var route = this.$root.$route
+    init: function () {
+      const route = this.$root.$route
       if (route) {
         route.router._children.push(this)
         if (!this.$route) {
-          if (this._defineMeta) {
-            // 0.12 compat
-            this._defineMeta('$route', route)
-          } else {
-            _.defineReactive(this, '$route', route)
-          }
+          _.defineReactive(this, '$route', route)
         }
       }
     },
     beforeDestroy: function () {
-      var route = this.$root.$route
+      const route = this.$root.$route
       if (route) {
         route.router._children.$remove(this)
       }
     }
   }
 
+  // pre 1.0.0-rc compat
+  if (!Vue.config.optionMergeStrategies ||
+      !Vue.config.optionMergeStrategies.init) {
+    delete mixin.init
+    const init = Vue.prototype._init
+    Vue.prototype._init = function (options) {
+      const root = options._parent || options.parent || this
+      const route = root.$route
+      if (route) {
+        route.router._children.push(this)
+        if (!this.$route) {
+          if (this._defineMeta) {
+            this._defineMeta('$route', route)
+          } else {
+            _.defineReactive(this, '$route', route)
+          }
+        }
+      }
+      init.call(this, options)
+    }
+  }
+
   if (Vue.mixin) {
     Vue.mixin(mixin)
   } else {