[improvement] extract relation mixin

packages/dropdown-item/index.js

@@ -2,34 +2,25 @@ import { use, isDef } from '../utils';
 import Cell from '../cell';
 import Icon from '../icon';
 import Popup from '../popup';
+import { ChildrenMixin } from '../mixins/relation';
 
 const [sfc, bem] = use('dropdown-item');
 
 export default sfc({
+  mixins: [ChildrenMixin('vanDropdownMenu')],
+
   props: {
     value: null,
     title: String,
     options: Array
   },
 
-  inject: ['vanDropdownMenu'],
-
   data() {
     return {
       show: false
     };
   },
 
-  created() {
-    const { items } = this.vanDropdownMenu;
-    const index = this.vanDropdownMenu.slots().indexOf(this.$vnode);
-    items.splice(index === -1 ? items.length : index, 0, this);
-  },
-
-  beforeDestroy() {
-    this.vanDropdownMenu.items = this.vanDropdownMenu.items.filter(item => item !== this);
-  },
-
   computed: {
     displayTitle() {
       if (this.title) {
@@ -48,7 +39,7 @@ export default sfc({
   },
 
   render(h) {
-    const { top, zIndex, activeColor } = this.vanDropdownMenu;
+    const { top, zIndex, activeColor } = this.parent;
 
     const Options = this.options.map(option => {
       const active = option.value === this.value;