fix(DatetimePicker): getPicker method not work (#5710)

src/datetime-picker/README.md

@@ -197,4 +197,4 @@ Use [ref](https://vuejs.org/v2/api/#ref) to get DatetimePicker instance and call
 
 | Name | Description | Attribute | Return value |
 |------|------|------|------|
-| getPicker `v2.4.0` | get Picker instance | - | - |
+| getPicker `v2.5.3` | get Picker instance | - | - |

src/datetime-picker/README.zh-CN.md

@@ -201,7 +201,7 @@ export default {
 
 | 方法名 | 说明 | 参数 | 返回值 |
 |------|------|------|------|
-| getPicker `v2.4.0` | 获取 Picker 实例，用于调用 Picker 的[实例方法](#/zh-CN/picker#fang-fa) | - | - |
+| getPicker `v2.5.3` | 获取 Picker 实例，用于调用 Picker 的[实例方法](#/zh-CN/picker#fang-fa) | - | - |
 
 ## 常见问题
 

src/datetime-picker/index.js

@@ -10,11 +10,19 @@ export default createComponent({
     ...DatePicker.props,
   },
 
+  methods: {
+    // @exposed-api
+    getPicker() {
+      return this.$refs.root.getPicker();
+    },
+  },
+
   render() {
     const Component = this.type === 'time' ? TimePicker : DatePicker;
 
     return (
       <Component
+        ref="root"
         class={bem()}
         {...{
           props: this.$props,

src/datetime-picker/test/datetime-picker.spec.js

@@ -30,3 +30,8 @@ test('time type', () => {
 
   expect(wrapper).toMatchSnapshot();
 });
+
+test('getPicker method', () => {
+  const wrapper = mount(DatetimePicker);
+  expect(wrapper.vm.getPicker()).toBeTruthy();
+});