promise - 无法在未定义的 Sequelize 错误上调用方法 'then'

Question

我在函数内返回一个 promise ，并在函数外处理 promise ，但我在未定义的错误上无法调用方法“then”。有人可以指出我做错了什么或如何解决这个问题。

function getMeterReadingByMeterIdandDate(sequelize, Dials, Meter, Server, meter_id, date){
   getNameByMeterId(sequelize, Meter, meter_id)
  .then(function(meter){
    getServerIdByMeterId(sequelize, Server, meter_id)
    .then(function(server){
      var name = meter[0].meter_id;
      var channel = "Ch"+name.substr(-1);
      var serialNumber = parseInt(name.substr(0,12));
      console.log({name:name,channel:channel,serialNumber:serialNumber});
      var server_id = server[0].server_id;
      return sequelize.query("select SUM(?) as total from dial?s where RealReadDate <= ? and SN = ?",
      {
        model:Dials[server_id],
        replacements:[channel, server_id, date.toISOString(), serialNumber],
        type: sequelize.QueryTypes.SELECT
      });
    });
  });
}


function getStartMeterReadingByMeterIdAndBillingId(sequelize, Dials, Billings, Meter, Server, meter_id, billing_id){
   getStartDateByBillingId(sequelize,Billings,billing_id)
  .then(function(date){
    return getMeterReadingByMeterIdandDate(sequelize, Dials, Meter, Server, meter_id, date[0].start_date);
  });
}

 getStartMeterReadingByMeterIdAndBillingId(sequelize, Dials, Billings, Meter, Servers, meter.id, billing_id)
            .then(function(current_date_result){
              meter_obj.current = current_date_result[0].total;
});

当我运行 callgetStartMeterReadingByMeterIdAndBillingId 时，我得到了无法调用方法 'then' 错误。我们是否允许返回像 than 这样的 Sequelize promise ，然后使用该函数处理 then else where。

Answer 1

getStartMeterReadingByMeterIdAndBillingId 函数不会根据您的代码示例返回 promise 。

假设 getStartDateByBillingId 返回一个 promise，您应该将代码更改为:

function getStartMeterReadingByMeterIdAndBillingId(sequelize, Dials, Billings, Meter, Server, meter_id, billing_id){
   return getStartDateByBillingId(sequelize,Billings,billing_id)
  .then(function(date){
    return getMeterReadingByMeterIdandDate(sequelize, Dials, Meter, Server, meter_id, date[0].start_date);
  });
}