小程序云开发 Collection.watch 监听器构建和销毁

// release/chatroom/index.js
const db = wx.cloud.database()
var musicwatcher = null
Page({
  onLoad: function (options) {
    this.musicwatcher = db.collection('MUSIC_LOG').where({
      playstatus:1
    }).watch({
      onChange: function (snapshot) {
        //只打印变动的信息
        // console.log(snapshot.docChanges)
        if (snapshot.docChanges.length != 0) {
          // console.log(snapshot.docChanges)
          that.setData({
            songInfo: snapshot.docChanges[0].doc
          })
        }
      },
      onError: function (err) {
        console.error('the watch closed because of error', err)
      }
    })
  },
  onUnload: function () {
    console.log('隐藏页面')
    //监听器销毁
    this.musicwatcher.close()
  }
})