promise - 如何在 Sails.js 中正确抛出和处理 promise 中的错误？

Question

我开始将回调代码转换为 Sails.js 中的 promise ，但我不明白如何在 promise 链中引发自定义错误并处理它们。 Sails.js 使用 Q 作为它的 promise 库。

User.findOne({email: req.param('professorEmail'), role: 'professor'})
    .then(function (user) {
      if (user) {
        return Course.create({
          user_id: user.id,
          section: req.param('section'),
          session: req.param('session'),
          course_code: req.param('course_code')
        });
      } else {
        // At this point `user` is undefined which means that no professor was found so I want to throw an error.
        // Right now the following statement does throw the error, but it crashes the server.
        throw new Error('That professor does not exist.');
        // I want to be able to handle the error in the .fail() or something similar in the promise chain.
      }
    }).then(function (createSuccess) {
      console.log(createSuccess);
    }).fail(function (err) {
      console.log(err);
    });

现在 .fail()永远不会被调用，因为抛出的错误会使服务器崩溃。

Answer 1

使用 .catch()而不是 .fail() .