Wechat applet cloud development 1 - Database

There are two most important aspects of wechat applet cloud development ：

1、 Cloud database ;

2、 Cloud functions ;

Learning these two points can basically carry out the cloud development of wechat applet ;

First , Let's first look at the basic operation of wechat applet cloud database ：

1） Open micro Letter developer tools , Create a cloud development wechat applet , Check use cloud development when creating a project ;( Be careful ： Using cloud development requires appId, Cannot use test number , Users who use cloud development for the first time need to open the cloud development function )

2） Click the cloud development option in the menu bar , Enter the cloud development control panel , Create a new development environment , Then click database , Create a new collection in the database of the current environment lists：

  Then click the data permission root in the database to configure the required database permissions ;

Detailed permissions visible ： Access control | Wechat open documents

3） In the project app.js Do the following configuration in ：

// app.js
App({
  onLaunch: function () {
    if (!wx.cloud) {
      console.error(' Please use  2.2.3  Or more base libraries to use cloud capabilities ');
    } else {
      wx.cloud.init({
        // env  Parameter description ：
        //   env  Parameters determine the next cloud development call initiated by the applet （wx.cloud.xxx） Which cloud environment resources will be requested by default 
        //    Please fill in the environment here  ID,  Environmental Science  ID  You can open the cloud console to view 
        //    If not, the default environment will be used （ First environment created ）
        env: ' The environment of the required development environment ID',
        traceUser: true,
      });
    }

    this.globalData = {};
  }
});

Environmental Science ID In this place ：

 4） Initialization, addition, deletion, modification and query of cloud database ：

Take the above database lists Set as an example ：

//  Initialize database 
const db = wx.cloud.database();
//  obtain   In the database lists aggregate 
const lists=db.collection('lists');

Insert ：

db.collection(' Collection name ').add({
   data:{
       // data  The field indicates the  JSON  data 
   }
}).then(res=>{console.log(res))

Throw out the following information, that is, the addition is successful ：

  Delete ：

db.collection(' Collection name ').doc(' To delete a field _id').remove().then(res=>{})

The deletion is successful when the following information is thrown ：

to update ：

db.collection(' Collection name ').doc(' The data that needs to be changed _id').update({
  // data  Pass in data that needs to be locally updated 
  data: {

  }
}).then(res=>{})

 eg:

const _ = db.command
db.collection('lists').doc('0ab5303b6286010904a878280d163117').update({
  data: {
    //  Indicates that the database will age Field auto increment  1
    age: _.inc(1)
  },
  success: function(res) {
    console.log(res.data)
  }
})

The following information is thrown to indicate that the update is successful ：

Inquire about ：

Query the data of a record ：

db.collection(' Collection name ').doc(' Of the data _id').get().then(res => {
  // res.data  Data containing the record 
  console.log(res.data)
})

Query... According to the conditions ：

db.collection(' Collection name ').where({
  //  Query criteria   Such as :
  age:18
}).get().then(res => {
  // res.data  contain age by 18 All data for 
  console.log(res.data)
})

Query sets all data ：

If you want to get the data of a collection , Like getting todos All records on the collection , You can call... On a collection  get  Method to get , But this is not usually recommended , In small programs, we need to try to avoid getting too much data at one time , Only necessary data should be obtained . In order to prevent misoperation and protect the applet experience , When the applet side obtains the collection data, the server defaults once and returns at most 20 Bar record , The number of cloud function end is 100. Developers can use  limit  Method to specify the number of records to get , But the applet side cannot exceed 20 strip , The cloud function end cannot exceed 100 strip .

db.collection(' Collection name ').get().then(res => {
  // res.data  Is a data that contains all records in the collection that have permission to access , No more than  20  strip 
  console.log(res.data)
})

The following is an example of getting a collection of all records on the cloud function side , Because at most one time 100 Restrictions on , Therefore, it is likely that one request cannot fetch all the data , It is necessary to take... In batches ：

const cloud = require('wx-server-sdk')
cloud.init()
const db = cloud.database()
const MAX_LIMIT = 100
exports.main = async (event, context) => {
  //  First, take out the total number of collection records 
  const countResult = await db.collection(' Collection name ').count()
  const total = countResult.total
  //  The calculation needs to be divided into several times 
  const batchTimes = Math.ceil(total / 100)
  //  Carrying all read operations  promise  Array of 
  const tasks = []
  for (let i = 0; i < batchTimes; i++) {
    const promise = db.collection(' Collection name ').skip(i * MAX_LIMIT).limit(MAX_LIMIT).get()
    tasks.push(promise)
  }
  //  Wait for all 
  return (await Promise.all(tasks)).reduce((acc, cur) => {
    return {
      data: acc.data.concat(cur.data),
      errMsg: acc.errMsg,
    }
  })
}

View more database manipulation statements ： initialization | Wechat open documents

more API see ： Wechat open documents