在这段代码中，我对两条路由有相同的逻辑，但它们的行为不同

Question

// @route   GET api/profile/handle/:handle
// @desc    Get profile by handle
// @access  Public

router.get('/handle/:handle', (req, res) => {
    const errors = {};

    Profile.findOne({ handle: req.params.handle })
        .populate('user', ['name', 'avatar'])
        .then(profile => {
            //console.log('profile1 ' + profile);
            if (!profile) {
                errors.noprofile = 'There is no profile for this user for handle route (from then block)';
                res.status(404).json(errors);
            }
            res.json(profile);
        })
        .catch(err => res.status(404).json({ profile: 'There is no profile for this user for handle route (from error block)' }));

});

// @route   GET api/profile/user/:user_id
// @desc    Get profile by user ID
// @access  Public

router.get('/user/:user_id', (req, res) => {
    const errors = {};

    Profile.findOne({ user: req.params.user_id })
        .populate('user', ['name', 'avatar'])
        .then(profile => {
            // console.log('profile not found by userid');
            //console.log('profile2 ' + profile);
            if (!profile) {
                errors.noprofile = 'There is no profile for this user for user_id route (from then block)';
                res.status(404).json(errors);
            }
            res.json(profile);
        })
        .catch(err => res.status(404).json({ profile: 'There is no profile for this user for user_id route (from error block)',
err: err }));
});

我有上述两条路线。第一个是使用句柄（用户名）从dB中搜索用户，第二个是使用dB本身创建的用户id进行搜索。当我使用错误的句柄请求第一条路由时，会执行then（）块，并得到以下响应：

{
    "noprofile": "There is no profile for this user for handle route (from then block)"
}

但在第二条路径（按用户id搜索）中，当我输入错误的用户id时，将执行catch块，并得到以下响应：

{
    "profile": "There is no profile for this user for user_id route (from error block)",
    "err": {
        "message": "Cast to ObjectId failed for value \"5cb0ec06d1d6f93c20874427rhdh\" at path \"user\" for model \"profile\"",
        "name": "CastError",
        "stringValue": "\"5cb0ec06d1d6f93c20874427rhdh\"",
        "kind": "ObjectId",
        "value": "5cb0ec06d1d6f93c20874427rhdh",
        "path": "user"
    }
}

这两条路线的逻辑相同，但它们的响应不同。这背后的原因是什么？？？

如果你想看看Profile模式，这里是：

const ProfileSchema = new Schema({
    user: {
        type: Schema.Types.ObjectId,
        ref: 'users'
    },
    handle: {
        type: String,
        required: true,
        max: 40
    },
    company: {
        type: String
    },
   ....
....
.....
});

我在使用错误句柄请求时也收到了警告，如下所示：

(node:16996) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:470:11)
    at ServerResponse.header (H:\MERN Stack Course\devConnector\node_modules\express\lib\response.js:767:10)
    at ServerResponse.send (H:\MERN Stack Course\devConnector\node_modules\express\lib\response.js:170:12)
    at ServerResponse.json (H:\MERN Stack Course\devConnector\node_modules\express\lib\response.js:267:15)
    at Profile.findOne.populate.then.catch.err (H:\MERN Stack Course\devConnector\routes\api\profile.js:75:39)
    at process._tickCallback (internal/process/next_tick.js:68:7)
(node:16996) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:16996) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Answer 1

我认为在您的第二个路由中，您试图使用无效的ObjectID进行查询。

请检查：什么是Mongoose错误Cast to ObjectId失败的值XXX在路径"_id"？

Answer 2

检查错误消息

"message": "Cast to ObjectId failed for value \"5cb0ec06d1d6f93c20874427rhdh\" at path \"user\" for model \"profile\""

user字段是mongob类型的ObjectId，您提供的是String，而句柄是类型String

对于handle查询，没有错误，只是db中没有条目。

你可以像猫鼬一样修复它。类型。ObjectId（req.params.user_id）.这里更多

还有，你的代码有问题。（执行不会在你认为停止的地方停止，你会得到未经处理的promise拒绝）

.then(profile => {
  //console.log('profile1 ' + profile);
  if (!profile) { // <--- if true
    errors.noprofile = 'There is no profile for this user for handle route (from then block)';
    res.status(404).json(errors); // <-- executes
  }
  res.json(profile); // <--- always executes within then callback
})

如果这个检查if（！配置文件）计算为true，然后执行res.status（404）. json（错误）。然后执行下一个res.json。

在您的代码中，res.json（profile）总是在没有错误时执行。您可以通过使用return停止执行或如果。。其他如：

return res.status(404).json(errors);

// or
if (!profile) {
  errors.noprofile = 'There is no profile for this user for handle route (from then block)';
  res.status(404).json(errors);
} else {
  res.json(profile);
}