使用 Formidable 上传 Node.js 文件 - 事件不会被触发

Question

我正在尝试使用 Node.js 和 Formidable 模块进行文件上传。

npm install formidable

然后我做了这个，请阅读注释 - 我可以解释每个函数的作用并描述算法：

// get access to the files that were sent;
// at this time I don't want the files to be uploaded yet;
// in the next function I will validate those files.
function form_parse() {
    form.parse(req, (err, fields, files) => {
      if (err) return req.Cast.error(err);
      if (Object.keys(files).length==0) return req.Cast.badRequest();
      req.files = files;
      return validate_files();
    });
  }

  // I made an object with options to validate against the
  // files. it works and continues to the process_files()
  // function only whether files are verified.
  function validate_files() {
    let limitations = require('../uploads-limitations');
    try {
      limitation = limitations[req.params.resource];
    } catch(err) {
      return req.Cast.error(err);
    }
    let validateFiles = require('../services/validate-files');
    validateFiles(req, limitation, err => {
      if (err) return req.Cast.badRequest(err);
      return process_files();
    });
  }

  // here is the problem - form.on doesn't get fired.
  // This is the time I want to save those files - after
  // fully verified
  function process_files() {
    form.on('file', function(name, file) {
      console.log(`file name: ${file.name}`);
      file.path = path.join(__dirname, '../tmp_uploads/' + file.name);
    });
    form.on('error', err => {
      return req.Cast.error(err);
    });
    form.on('end', () => {
      console.log(`successfully saved`);
      return req.Cast.ok();
    });
  }

  form_parse();

如您所见和我所描述的 - 验证有效，但是当我想实际保存这些文件时，form.on（事件）不会被触发。

Answer 1

是的，因为在您的流程结束时，在解析和验证之后，您附加了事件侦听器。这应该在开始解析之前首先完成。因为这些事件（存档、错误、结束）发生在解析期间，而不是之后。

 form.on('file',...) // First, attach your listeners
    .on('error', ...)
    .on('end', ...);

form.parse(req) // then start the parsing