From 7f4ad6a28d731abbfa4a3b08b4c5caf8adcdc93d Mon Sep 17 00:00:00 2001
From: neverland <chenjiahan@buaa.edu.cn>
Date: Tue, 3 Jul 2018 23:36:36 +0800
Subject: [PATCH] [Improvement] Picker: optimize render performance (#1391)

---
 packages/picker/PickerColumn.vue              | 24 +++------
 packages/picker/index.vue                     | 53 +++++++++++--------
 .../test/__snapshots__/demo.spec.js.snap      | 10 ++--
 .../test/__snapshots__/index.spec.js.snap     | 15 +-----
 packages/picker/test/index.spec.js            | 12 ++---
 5 files changed, 50 insertions(+), 64 deletions(-)

diff --git a/packages/picker/PickerColumn.vue b/packages/picker/PickerColumn.vue
index 92b484b43..29cfecc96 100644
--- a/packages/picker/PickerColumn.vue
+++ b/packages/picker/PickerColumn.vue
@@ -25,6 +25,7 @@
 
 <script>
 import create from '../utils/create';
+import deepClone from '../utils/deep-clone';
 import { isObj } from '../utils';
 
 const DEFAULT_DURATION = 200;
@@ -38,7 +39,7 @@ export default create({
     className: String,
     itemHeight: Number,
     visibleItemCount: Number,
-    options: {
+    initialOptions: {
       type: Array,
       default: () => []
     },
@@ -54,15 +55,13 @@ export default create({
       offset: 0,
       duration: 0,
       startOffset: 0,
+      options: deepClone(this.initialOptions),
       currentIndex: this.defaultIndex
     };
   },
 
   created() {
     this.$parent.children && this.$parent.children.push(this);
-  },
-
-  mounted() {
     this.setIndex(this.currentIndex);
   },
 
@@ -73,12 +72,6 @@ export default create({
   watch: {
     defaultIndex() {
       this.setIndex(this.defaultIndex);
-    },
-
-    options(next, prev) {
-      if (JSON.stringify(next) !== JSON.stringify(prev)) {
-        this.setIndex(0);
-      }
     }
   },
 
@@ -103,10 +96,6 @@ export default create({
         transform: `translate3d(0, ${this.offset + this.baseOffset}px, 0)`,
         lineHeight: this.itemHeight + 'px'
       };
-    },
-
-    currentValue() {
-      return this.options[this.currentIndex];
     }
   },
 
@@ -168,10 +157,13 @@ export default create({
       const { options } = this;
       for (let i = 0; i < options.length; i++) {
         if (this.getOptionText(options[i]) === value) {
-          this.setIndex(i);
-          return;
+          return this.setIndex(i);
         }
       }
+    },
+
+    getValue() {
+      return this.options[this.currentIndex];
     }
   }
 });
diff --git a/packages/picker/index.vue b/packages/picker/index.vue
index 7cc11c68f..437cad03a 100644
--- a/packages/picker/index.vue
+++ b/packages/picker/index.vue
@@ -12,10 +12,10 @@
     </div>
     <div :class="b('columns')" :style="columnsStyle" @touchmove.prevent>
       <picker-column
-        v-for="(item, index) in currentColumns"
+        v-for="(item, index) in (simple ? [columns] : columns)"
         :key="index"
         :value-key="valueKey"
-        :options="item.values"
+        :initial-options="simple ? item : item.values"
         :class-name="item.className"
         :default-index="item.defaultIndex"
         :item-height="itemHeight"
@@ -65,22 +65,10 @@ export default create({
 
   data() {
     return {
-      children: [],
-      currentColumns: []
+      children: []
     };
   },
 
-  watch: {
-    columns: {
-      handler() {
-        const columns = this.columns.map(deepClone);
-        this.isSimpleColumn = columns.length && !columns[0].values;
-        this.currentColumns = this.isSimpleColumn ? [{ values: columns }] : columns;
-      },
-      immediate: true
-    }
-  },
-
   computed: {
     frameStyle() {
       return {
@@ -92,12 +80,29 @@ export default create({
       return {
         height: this.itemHeight * this.visibleItemCount + 'px'
       };
+    },
+
+    simple() {
+      return this.columns.length && !this.columns[0].values;
+    }
+  },
+
+  watch: {
+    columns() {
+      this.setColumns();
     }
   },
 
   methods: {
+    setColumns() {
+      const columns = this.simple ? [{ values: this.columns }] : this.columns;
+      columns.forEach((columns, index) => {
+        this.setColumnValues(index, deepClone(columns.values));
+      });
+    },
+
     emit(event) {
-      if (this.isSimpleColumn) {
+      if (this.simple) {
         this.$emit(event, this.getColumnValue(0), this.getColumnIndex(0));
       } else {
         this.$emit(event, this.getValues(), this.getIndexes());
@@ -105,7 +110,7 @@ export default create({
     },
 
     onChange(columnIndex) {
-      if (this.isSimpleColumn) {
+      if (this.simple) {
         this.$emit('change', this, this.getColumnValue(0), this.getColumnIndex(0));
       } else {
         this.$emit('change', this, this.getValues(), columnIndex);
@@ -119,7 +124,8 @@ export default create({
 
     // get column value by index
     getColumnValue(index) {
-      return (this.getColumn(index) || {}).currentValue;
+      const column = this.getColumn(index);
+      return column && column.getValue();
     },
 
     // set column value by index
@@ -141,20 +147,21 @@ export default create({
 
     // get options of column by index
     getColumnValues(index) {
-      return (this.currentColumns[index] || {}).values;
+      return (this.children[index] || {}).options;
     },
 
     // set options of column by index
     setColumnValues(index, options) {
-      const column = this.currentColumns[index];
-      if (column) {
-        column.values = options;
+      const column = this.children[index];
+      if (column && JSON.stringify(column.options) !== JSON.stringify(options)) {
+        column.options = options;
+        column.setIndex(0);
       }
     },
 
     // get values of all columns
     getValues() {
-      return this.children.map(child => child.currentValue);
+      return this.children.map(child => child.getValue());
     },
 
     // set values of all columns
diff --git a/packages/picker/test/__snapshots__/demo.spec.js.snap b/packages/picker/test/__snapshots__/demo.spec.js.snap
index 435f9cc51..af55401c9 100644
--- a/packages/picker/test/__snapshots__/demo.spec.js.snap
+++ b/packages/picker/test/__snapshots__/demo.spec.js.snap
@@ -26,9 +26,9 @@ exports[`renders demo correctly 1`] = `
       <!---->
       <div class="van-picker__columns" style="height:220px;">
         <div class="van-picker-column" style="height:220px;">
-          <ul style="transition:0ms;transform:translate3d(0, 88px, 0);line-height:44px;">
-            <li class="van-ellipsis van-picker-column__item van-picker-column__item--disabled van-picker-column__item--selected">杭州</li>
-            <li class="van-ellipsis van-picker-column__item">宁波</li>
+          <ul style="transition:0ms;transform:translate3d(0, 44px, 0);line-height:44px;">
+            <li class="van-ellipsis van-picker-column__item van-picker-column__item--disabled">杭州</li>
+            <li class="van-ellipsis van-picker-column__item van-picker-column__item--selected">宁波</li>
             <li class="van-ellipsis van-picker-column__item">温州</li>
           </ul>
         </div>
@@ -70,7 +70,7 @@ exports[`renders demo correctly 1`] = `
           </ul>
         </div>
         <div class="van-picker-column column2" style="height:220px;">
-          <ul style="transition:0ms;transform:translate3d(0, 88px, 0);line-height:44px;">
+          <ul style="transition:0ms;transform:translate3d(0, 0px, 0);line-height:44px;">
             <li class="van-ellipsis van-picker-column__item">杭州</li>
             <li class="van-ellipsis van-picker-column__item">宁波</li>
             <li class="van-ellipsis van-picker-column__item van-picker-column__item--selected">温州</li>
@@ -96,7 +96,7 @@ exports[`renders demo correctly 1`] = `
           </ul>
         </div>
         <div class="van-picker-column column2" style="height:220px;">
-          <ul style="transition:0ms;transform:translate3d(0, 88px, 0);line-height:44px;">
+          <ul style="transition:0ms;transform:translate3d(0, 0px, 0);line-height:44px;">
             <li class="van-ellipsis van-picker-column__item">杭州</li>
             <li class="van-ellipsis van-picker-column__item">宁波</li>
             <li class="van-ellipsis van-picker-column__item van-picker-column__item--selected">温州</li>
diff --git a/packages/picker/test/__snapshots__/index.spec.js.snap b/packages/picker/test/__snapshots__/index.spec.js.snap
index 8056267a1..78ef8d19f 100644
--- a/packages/picker/test/__snapshots__/index.spec.js.snap
+++ b/packages/picker/test/__snapshots__/index.spec.js.snap
@@ -18,8 +18,8 @@ exports[`column watch default index 2`] = `
 <div class="van-picker-column">
   <ul style="line-height: 50px;">
     <li class="van-ellipsis van-picker-column__item van-picker-column__item--disabled">1</li>
-    <li class="van-ellipsis van-picker-column__item van-picker-column__item--selected">1990</li>
-    <li class="van-ellipsis van-picker-column__item">1991</li>
+    <li class="van-ellipsis van-picker-column__item">1990</li>
+    <li class="van-ellipsis van-picker-column__item van-picker-column__item--selected">1991</li>
     <li class="van-ellipsis van-picker-column__item">1992</li>
     <li class="van-ellipsis van-picker-column__item">1993</li>
     <li class="van-ellipsis van-picker-column__item">1994</li>
@@ -27,14 +27,3 @@ exports[`column watch default index 2`] = `
   </ul>
 </div>
 `;
-
-exports[`column watch default index 3`] = `
-<div class="van-picker-column">
-  <ul style="line-height: 50px;">
-    <li class="van-ellipsis van-picker-column__item van-picker-column__item--selected">1</li>
-    <li class="van-ellipsis van-picker-column__item van-picker-column__item--disabled">1</li>
-    <li class="van-ellipsis van-picker-column__item van-picker-column__item--disabled">1</li>
-    <li class="van-ellipsis van-picker-column__item van-picker-column__item--disabled">1</li>
-  </ul>
-</div>
-`;
diff --git a/packages/picker/test/index.spec.js b/packages/picker/test/index.spec.js
index 4303020ce..66c680d02 100644
--- a/packages/picker/test/index.spec.js
+++ b/packages/picker/test/index.spec.js
@@ -1,6 +1,6 @@
 import Picker from '../';
 import PickerColumn from '../PickerColumn';
-import { mount, triggerDrag } from '../../../test/utils';
+import { mount, triggerDrag, later } from '../../../test/utils';
 
 const simpleColumn = ['1990', '1991', '1992', '1993', '1994', '1995'];
 const columns = [
@@ -101,21 +101,19 @@ test('drag simple columns', () => {
   expect(wrapper.emitted('change')[0][1]).toEqual('1992');
 });
 
-test('column watch default index', () => {
+test('column watch default index', async() => {
   const disabled = { disabled: true, text: 1 };
   const wrapper = mount(PickerColumn, {
     propsData: {
+      initialOptions: [disabled, ...simpleColumn],
       valueKey: 'text',
       itemHeight: 50
     }
   });
-  wrapper.vm.options = [disabled, ...simpleColumn];
+
+  await later();
   expect(wrapper).toMatchSnapshot();
 
-  wrapper.vm.options = [disabled, ...simpleColumn];
-  expect(wrapper).toMatchSnapshot();
-
-  wrapper.vm.options = [1, disabled, disabled, disabled];
   wrapper.vm.defaultIndex = 2;
   expect(wrapper).toMatchSnapshot();
 });