表达承诺链如何发送响应并终止承诺链流程？

Question

With the code below i'm getting this error:

Unhandled rejection Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client if result === null .

'use strict'

const HttpStatus = require('http-status-codes')
const { handleErr } = require('ciitizen-express-helpers').utils

function updateOrganization(db, stats) {
  return function (req, res) {
    db.organization.findOne({
      where: {
        id: req.params.id
      }
    })
      .then(result => {

        if (result === null) {
          return res.status(HttpStatus.NOT_FOUND).send() <-- IF RESULT IS NULL, I RETURN THIS 
        }

        console.log('original result = ', result)

        // Update any fields that were passed in
        if (req.body.name) {
          result.name = req.body.name
        }

        if (req.body.address1) {
          result.address1 = req.body.address1
        }

        if (req.body.address2) {
          result.address2 = req.body.address2
        }

        if (req.body.city) {
          result.city = req.body.city
        }

        if (req.body.state) {
          result.state = req.body.state
        }

        if (req.body.zip) {
          result.zip = req.body.zip
        }

        console.log('new result = ', result)
        return result.save()
      })
      .then(result => {
        console.log('final result = ', result)
        return res.status(HttpStatus.CREATED).send(result) <-- BUT IT'S STILL TRYING TO CALL THIS, HENCE THE CAN'T SEND HEADERS ERROR
      })
      .catch(err => {
        req.log.error(err)
        return handleErr(res, HttpStatus.INTERNAL_SERVER_ERROR, err.message)
      })
  }
}

module.exports = updateOrganization

What's the best way to return a response early without continuing through my promise chain flow?

Answer 1

Promises chain like that

What you can do is

A) return null AFTER res.status(HttpStatus.NOT_FOUND) (removing the return before that code)

B) in then(result check if result is null, if so, skip the res.status(... code

eg

'use strict'

const HttpStatus = require('http-status-codes')
const { handleErr } = require('ciitizen-express-helpers').utils

function updateOrganization(db, stats) {
  return function (req, res) {
    db.organization.findOne({
      where: {
        id: req.params.id
      }
    })
      .then(result => {

        if (result === null) {
          // change A
          res.status(HttpStatus.NOT_FOUND).send();
          return null;
        }
        // snip
        return result.save()
      })
      .then(result => {
        console.log('final result = ', result)
        // change B
        if (result !== null) {
            return res.status(HttpStatus.CREATED).send(result)
        }
      })
      .catch(err => {
        req.log.error(err)
        return handleErr(res, HttpStatus.INTERNAL_SERVER_ERROR, err.message)
      })
  }
}

module.exports = updateOrganization

alternatively, keep your existing code until

      .then(result => {
        // change C
        if (!res.headersSent) {
            console.log('final result = ', result)
            return res.status(HttpStatus.CREATED).send(result)
        }
      })

That's probably a "cleaner" fix to be honest

Answer 2

Test this:

    function updateOrganization(db, stats) {
  return function (req, res) {
    db.organization.findOne({
      where: {
        id: req.params.id
      }
    })
      .then(result => {

        if (!result) {
          res.status(HttpStatus.NOT_FOUND).end();
          return null;
        }

        console.log('original result = ', result)

        // Update any fields that were passed in
        if (req.body.name) {
          result.name = req.body.name
        }

        if (req.body.address1) {
          result.address1 = req.body.address1
        }

        if (req.body.address2) {
          result.address2 = req.body.address2
        }

        if (req.body.city) {
          result.city = req.body.city;
        }

        if (req.body.state) {
          result.state = req.body.state;
        }

        if (req.body.zip) {
          result.zip = req.body.zip;
        }

        console.log('new result = ', result);
        return result.save();
      })
      .then(result => {
        console.log('final result = ', result);
        if(result) {
            return res.status(HttpStatus.CREATED).json(result)
        }
        return null;

      })
      .catch(err => {
        req.log.error(err);
        return handleErr(res, HttpStatus.INTERNAL_SERVER_ERROR, err.message);
      })
  }
}