javascript - Node promise 链 : Local functions and how to pass multiple values (code-review)

Question

考虑到以下代码，我有以下问题:

#1这些 bluebird.all 函数返回的值需要在后面的函数中可以访问。从我读过的内容来看，我也可以使用 this-context，而无需事先声明变量。但是我在访问嵌套函数中的这些值时遇到了一些问题。

#2spread 方法是为了使这些参数在后续函数中可访问吗？

#3由于这些函数只在 main 方法中工作，它们应该像这样嵌套吗？

#4我找不到更好的条件 promise 链执行解决方案。如果有的话，我更喜欢一个不那么冗长的解决方案。

#5与 #3 相同，但这次嵌套在嵌套函数中。

function create(contactRequestPayload) {

  // #1 Local variables vs this
  var
    contactRequest = {},
    property = {};

  return bluebird.all([
    new ContactRequestModel(contactRequestPayload).save(),
    getPropertyById(contactRequestPayload.propertyId),
    sendContactMail()
  ])
    // #2 Correct usage of spread
    .spread(function (_contactRequest, _property) {
      contactRequest = _contactRequest;
      property = _property;
    })
    .then(processFeedbackEmail)
    .then(updateModelState)
    .then(returnContactRequest)
    .catch(errorHandler);

  // #3 Nested functions
  function processFeedbackEmail() {
    // #4 Conditional code execution
    if (!_.get(property, "contact.email.feedback")) {
      return bluebird.resolve();
    }

    return createFeedbackObject()
      .then(convertToXml)
      .then(sendFeedbackMail)
      .catch(function (error) {
        logger.warn(error);
      });

    // #5 Nested functions within a nested function        
    function createFeedbackObject() {
      return contactRequestFeedbackObjectService.from(property, contactRequest);
    }

    function convertToXml(contactFeedbackObject) {
      contactRequest.feedbackJson = contactFeedbackObject;
      return objectToXmlService.convert(contactFeedbackObject);
    }

    function sendFeedbackMail(contactFeedbackXml) {
      contactRequest.feedbackXml = contactFeedbackXml;
      return contactRequestFeedbackMailService.send(property.contact.email.feedback, contactFeedbackXml);
    }
  }

  function returnContactRequest() {
    return contactRequest;
  }

  function sendContactMail() {
    return searchServiceClient.sendContactMail(contactRequestPayload);
  }

  function getPropertyById(propertyId) {
    return getPropertyServiceClient().fetchPropertyById(propertyId);
  }

  function updateModelState() {
    contactRequest.state = 'SENT';
    return contactRequest.save();
  }
}

Answer 1

Promise 链让我们可以在前向流中像同步代码一样对事物进行排序。我发现内联函数重新获得了重要的上下文。为了使用之前的变量，我使用了很好的旧缩进:

function create(contactRequestPayload) {
  return bluebird.all([
    new ContactRequestModel(contactRequestPayload).save(),
    getPropertyServiceClient().fetchPropertyById(contactRequestPayload.propertyId),
    searchServiceClient.sendContactMail(contactRequestPayload)
  ])
  .spread(function processFeedbackEmail(contactRequest, property) {
    if (_.get(property, "contact.email.feedback")) {
      return contactRequestFeedbackObjectService.from(property, contactRequest)
      .then(function convertToXml(feedback) {
        contactRequest.feedbackJson = feedback;
        return objectToXmlService.convert(feedback);
      })
      .then(function sendFeedbackMail(xml) {
        contactRequest.feedbackXml = xml;
        return CRFeedbackMailService.send(property.contact.email.feedback, xml);
      })
      .catch(function (error) {
        logger.warn(error);
      });
    }
  })
  .then(function updateModelState() {
    contactRequest.state = 'SENT';
    return contactRequest.save();
  })
  .then(function returnContactRequest() {
    return contactRequest;
  })
  .catch(errorHandler);
}

(函数名称当然是可选的，但我保留了它们以供引用。)

对于条件，我将其反转，因为返回 undefined 等于 bluebird.resolve()。

有些人可能会争辩说这是一个风格问题，但 ES7 自然而然地得出了这个类比:

async function create(contactRequestPayload) {
  var [ contactRequest, property ] = await Promise.all([
    new ContactRequestModel(contactRequestPayload).save(),
    getPropertyServiceClient().fetchPropertyById(contactRequestPayload.propertyId),
    searchServiceClient.sendContactMail(contactRequestPayload)
  ]);
  if (_.get(property, "contact.email.feedback")) {
    try {
      var feedback = await contactRequestFeedbackObjectService.from(property,
                                                                    contactRequest);
      contactRequest.feedbackJson = feedback;
      contactRequest.feedbackXml = await objectToXmlService.convert(feedback);
      await CRFeedbackMailService.send(property.contact.email.feedback, xml);
    } catch (error) {
      logger.warn(error);
    }
  }
  contactRequest.state = 'SENT';
  await contactRequest.save();
  return contactRequest;
}