如何return mysql data to caller？有些东西有效，其他情况不起作用？

Question

这是我的数据库对象代码(DBO.js):

class DBO
{
    constructor(){
        let dbConfig = require('./config');
        dbConfig["multipleStatements"]=true;
        const moment = require('moment');
        const mysql = require('mysql2');
        const connection = mysql.createConnection(dbConfig);
        
        this.getITOList=(year,month,callBack)=>{
            const startDateString=year+"-"+month+"-01";
            const endDateString=moment(startDateString).add(1,"M").add(-1,"d").format('YYYY-MM-DD');
            
            let sqlString ="SELECT join_date,leave_date,ito_info.ito_id,post_name,ito_name,available_shift,working_hour_per_day,black_list_pattern from ";
            sqlString+="ito_info inner join black_list_pattern ";
            sqlString+="on ito_info.ito_id=black_list_pattern.ito_id ";
            sqlString+="where join_date<=? and leave_date >=? ";
            sqlString+="order by ito_info.ito_id";
            console.log("startDateString="+startDateString+",endDateString="+endDateString);
            connection.execute(sqlString,[startDateString,endDateString],(err, results, fields)=>{
                connection.end(err=>{
                    if (err) {
                        throw err;
                    } else {
                        callBack(err,results);
                        console.log("Get ITO List successfully.");
                    }
                });
            });
            
        }
        this.getRosterRule=(callBack)=>{
            let sqlString ="select * from roster_rule order by rule_type,rule_key,rule_value";
            connection.execute(sqlString,(err, results, fields)=>{
                connection.end(err=>{
                    if (err) {
                        throw err;
                    } else {
                        callBack(err,results);
                        console.log("Get Roster Rule successfully!");
                    }
                });
            });
        }
        this.close=()=>{
            connection.end(err=>{
                if (err) throw err;
                console.log("Disconnect form "+process.env["DATABASE_HOST"]+" successfully!");
            });
        }       
    }
}
module.exports = DBO;

这是 RosterRule 对象：

class RosterRule{
    constructor(){
        let DBO=require("../utils/dbo.js");
        let dboObj=new DBO();
        this.essentialShiftList=null;   
        this.maxConsecutiveWorkingDay=0;
        this.shiftHourCount={};     
        dboObj.getRosterRule((err,resultList)=>{
            if (err){
                throw err;
            }else {
                resultList.forEach(result=>{
                    switch (result.rule_type){
                        case 'ConsecutiveWorkingDay':
                            this.maxConsecutiveWorkingDay=parseInt(result.rule_value);
                            break;
                        case 'shiftHour':
                            this.shiftHourCount[result.rule_key]=parseFloat(result.rule_value);
                            break;
                        case 'shiftList':
                            var temp=result.rule_value.replace(/"/g,'');
                            this.essentialShiftList=temp.split(',');
                            break;
                    }
                });
            }
        });
        
    }
}
module.exports =new RosterRule();

这是一个 ITO 对象。

class ITO
{
    constructor(){
        /**
         * The ITO Id of the specified ITO.
         */
        this.itoId="";
        /**
         * The name of the specified ITO.
         */
        this.itoName="";
        /**
         * The post name of the specified ITO
         */
        this.postName="";
    
        /**
         * The total no. of working hour per day for the specified ITO.
         */
        this.workingHourPerDay=0.0;
        /**
         * The join date of the specified ITO.
         */
        this.joinDate=null;
        /**
         * The leave date of the specified ITO.
         */
        this.leaveDate=null;
        /**
         * The available shift list of the specified ITO.   
         */
        this.availableShiftList=[];
        /**
         * The black listed shift pattern list of the specified ITO.    
         */
        this.blackListedShiftPatternList=[];        
    }
    static getITOList(year, month){
        let DBO=require("../utils/dbo.js");
        let dboObj=new DBO();
        let resultObj={};
        dboObj.getITOList(year,month,(err,resultList)=>{
            if (err){
                throw err;
            }else {
                resultList.forEach(ito=>{
                    let itoObj;
                    if (resultObj[ito.ito_id]){
                        itoObj=resultObj[ito.ito_id];
                        itoObj.blackListedShiftPatternList.push(ito.black_list_pattern);
                    }else {
                        itoObj=new ITO();
                        itoObj.itoId=ito.ito_id;
                        itoObj.itoName=ito.ito_name;
                        itoObj.postName=ito.post_name;
                        itoObj.workingHourPerDay=ito.working_hour_per_day;
                        itoObj.joinDate=new Date(ito.join_date);
                        itoObj.leaveDate=new Date(ito.leave_date);
                        itoObj.availableShiftList=ito.available_shift.split(",");
                        itoObj.blackListedShiftPatternList.push(ito.black_list_pattern);
                    }
                    resultObj[ito.ito_id]=itoObj;
                });
                console.log("hi:"+JSON.stringify(resultObj));
                return resultObj;               
            }
        });
        
    }
}
module.exports = ITO;

最后，这是 RosterManager 对象代码：

class RosterManager
{
    constructor(){
        let DBO=require("../utils/dbo.js");
        let ITO=require("./ITO.js");
        const RosterRule = require('./RosterRule');
        this.getRosterList=(year,month)=>{
            console.log("RosterRule:"+RosterRule);
            let itoList=ITO.getITOList(year,month);
            console.log(itoList);
        }
    }
}
module.exports = RosterManager;

可以从数据库成功加载所有 RosterRule 属性。

调用RosterManager.getRosterList时，为什么return值为“未定义”？

我在ITO中添加了如下语句，DBO对象从DB中获取数据成功

console.log("hi:"+JSON.stringify(resultObj));

但是，在RosterManager对象中无法读取数据。

你能帮忙修一下吗？

Answer 1

将查询包装在承诺中。还要避免在代码中添加 require()。而是将其保留在文件的开头，而不是在代码执行过程中调用它。

此外，如果您要使用这么多 classes，可以考虑使用 typescript 键入所有内容。

在伊藤class:

static getITOList(year, month){
  let DBO=require("../utils/dbo.js");
  let dboObj=new DBO();
  let resultObj={};
  return new Promise((resolve, reject) => {
    dboObj.getITOList(year,month,(err,resultList)=>{
      if (err){
          reject(err);
      } {
          resultList.forEach(ito=>{
              let itoObj;
              if (resultObj[ito.ito_id]){
                  itoObj=resultObj[ito.ito_id];
                  itoObj.blackListedShiftPatternList.push(ito.black_list_pattern);
              }else {
                  itoObj=new ITO();
                  itoObj.itoId=ito.ito_id;
                  itoObj.itoName=ito.ito_name;
                  itoObj.postName=ito.post_name;
                  itoObj.workingHourPerDay=ito.working_hour_per_day;
                  itoObj.joinDate=new Date(ito.join_date);
                  itoObj.leaveDate=new Date(ito.leave_date);
                  itoObj.availableShiftList=ito.available_shift.split(",");
                  itoObj.blackListedShiftPatternList.push(ito.black_list_pattern);
              }
              resultObj[ito.ito_id]=itoObj;
          });
          console.log("hi:"+JSON.stringify(resultObj));
          resolve(resultObj);               
      }
    });
  });
}

在名册管理器中

constructor(){
  let DBO=require("../utils/dbo.js");
  let ITO=require("./ITO.js");
  const RosterRule = require('./RosterRule');
  this.getRosterList=(year,month)=>{
      console.log("RosterRule:"+RosterRule);
      ITO.getITOList(year, month).then(itoList => {
        console.log(itoList);
      }).catch(err => {
        // handle error
      });
  }
}