小程序自定义组件中observer函数的应用

<!-- 单个数据监听 -->
<view>白菜</view>
<view>价格：{{price}}</view>
<!-- bindinput输入时触发方法 -->
<view>数量： <input type="number"  bindinput='changee' value="{{num1}}"></input></view>
<view>总价：{{sum}}</view><!-- 多个数据监听 -->
<view class='sum2'>
<input class='inlineInput' type="number"  bindinput='changeNum2' value="{{num2}}"></input>+
<input class='inlineInput' type="number"  bindinput='changeNum3' value="{{num3}}"></input>=
<text>{{sum2}}</text>
</view>

js

// components/date/index.js
Component({/*** 组件的属性列表*/properties: {},/*** 组件的初始数据*/data: {num1: 0,sum:0,price: 2,num2: 0,num3: 0,sum2: 0},/*** 组件的方法列表*/methods: {changee(e){// console.log(e);let num1 = e.detail.value;this.setData({num1: num1})},changeNum2(e){let num2 = e.detail.value;this.setData({num2: num2})},changeNum3(e) {let num3 = e.detail.value;this.setData({num3: num3})}},observers: { //观察者：属性监听//单个监听'num1'(num1) {  this.setData({sum: num1*this.data.price})},//多个监听'num2,num3'(num2,num3){num2 == '' && (num2 = 0);num3 == '' && (num3 = 0);this.setData({sum2: parseFloat(num2) + parseFloat(num3)})  }}})