feat(TreeSelect): add max prop (#2004)

example/pages/tree-select/index.wxml

@@ -16,6 +16,7 @@
     active-id="{{ activeIdMulti }}"
     bind:click-item="onClickItemMulti"
     bind:click-nav="onClickNavMulti"
+    max="2"
     content-item-class="content-item-class"
   ></van-tree-select>
 </demo-block>

packages/tree-select/README.md

@@ -97,6 +97,7 @@ Page({
 | items | 分类显示所需的数据 | *Array* | `[]` |  - |
 | main-active-index | 左侧选中项的索引 | *number* | `0` | - |
 | active-id | 右侧选中项的 id，支持传入数组 | *string \| number \| Array* | `0` | - |
+| max | 右侧项最大选中个数 | *number* | *Infinity* | - |
 
 ### Events
 

packages/tree-select/index.ts

@@ -23,6 +23,10 @@ VantComponent({
     maxHeight: {
       type: Number,
       value: 300
+    },
+    max: {
+      type: Number,
+      value: Infinity
     }
   },
 
@@ -51,7 +55,13 @@ VantComponent({
     // 当一个子项被选择时
     onSelectItem(event: Weapp.Event) {
       const { item } = event.currentTarget.dataset;
-      if (!item.disabled) {
+      const isArray = Array.isArray(this.data.activeId);
+      // 判断有没有超出右侧选择的最大数
+      const isOverMax = isArray && (this.data.activeId.length >= this.data.max);
+      // 判断该项有没有被选中, 如果有被选中，则忽视是否超出的条件
+      const isSelected = isArray ? this.data.activeId.indexOf(item.id) > -1 : this.data.activeId === item.id;
+
+      if (!item.disabled && (!isOverMax || isSelected)) {
         this.$emit('click-item', item);
       }
     },