Question

我的开发服务器崩溃了，无法重启。当我查看日志时，收到以下消息。下面是错误

from itertools import count

for i in count():
    print(i)
    # don't run this without some mechanism to break the loop, i.e.
    # if i == 10:
    #     break

# OUTPUT
# 0
# 1
# 2
# ...and so on

此消息仅在生产中出现，而不在开发中出现，这使我感到困惑。这是来自app / routes / index.js文件的相关代码

throw er; // Unhandled 'error' event
 TypeError: Cannot read property '_id' of null
    at /app/routes/index.js:220:53
    at model.Query.<anonymous>(/app/node_modules/mongoose/lib/model.js:4092:16)
    at /app/node_modules/kareem/index.js:273:21
    at /app/node_modules/kareem/index.js:131:16
    at process._tickCallback (internal/process/next_tick.js:61:11)
Emitted 'error' event at:
     at model.Query.<anonymous(/app/node_modules/mongoose/lib/model.js:4094:13)
     at /app/node_modules/kareem/index.js:273:21
     at /app/node_modules/kareem/index.js:131:16
     at process._tickCallback (internal/process/next_tick.js:61:11)

我在下面包括了我的评论架构。我尝试使用此解决方案node js returns undefined from mongodb obejct inner value，但不适用于这种情况。

// USER PROFILE
router.get("/users/:id", function(req, res) {
  User.findById(req.params.id, function(err, foundUser) {
    if(err) {
      req.flash("error", "Something went wrong.");
      res.redirect("/");
    }
Line 220 Comment.find().where('author').equals(foundUser._id).exec(function(err, comments) {
      if(err) {
        req.flash("error", "Something went wrong.");
        res.redirect("/");
      }
        res.render("show", {user: foundUser, comments: comments});
      })
    });
  });

编辑：基于评论中的讨论，我进行了一些测试，使我也能发现开发中出现的错误。我console.logged输出，这就是我得到的。

var mongoose = require("mongoose");

var CommentSchema = mongoose.Schema({
    text: String,
    created: 
        {type: Date, default: Date.now}, 
     author: {
        type: mongoose.Schema.Types.ObjectId,
        ref: "User"
    },
    blog: String
 });

 // pre-hook middleware to populate author in comment show route
CommentSchema.pre('findOne', function(next) {
 this.populate('author');
  next();
});

module.exports = mongoose.model("Comment", CommentSchema);

当时我以管理员用户身份登录。然后，我测试了console.log（req.params）

    This is the id { _id: 5af9af45f5a3b31bd4492e9d,
  username: 'mrboston',
  firstName: 'Mr',
  lastName: 'Boston',
  email: 'fake@yahoo.com',
  avatar: 'google.com',
  __v: 0,
  isAdmin: true }
This is the id undefined
events.js:160
      throw er; // Unhandled 'error' event
      ^

TypeError: Cannot read property '_id' of undefined

这是否意味着我对req.params查询的了解不够具体？

编辑2：

代码已更新为此：

{ id: '5af9af45f5a3b31bd4492e9d' }
{ id: 'google.com' }
events.js:160
      throw er; // Unhandled 'error' event

但是运行该应用程序并单击显示用户链接，我会收到此错误消息

// USER PROFILE
router.get("/users/:id", function(req, res) {
  User.findById(req.params.id, function(err, foundUser) {
    if(err) {
      req.flash("error", "Something went wrong.");
      res.redirect("/");
    }
    if (!foundUser) {
    Comment.find().where('author').equals(foundUser._id).exec(function(err, comments) {
      if(err) {
        req.flash("error", "Something went wrong.");
        res.redirect("/");
      }
        res.render("show", {user: foundUser, comments: comments});
      });
    }
    });
  });

编辑3：UserSchema

<html>
  <head>
    <meta charset='utf-8'> 
    <title>Error 502 - Bad Gateway</title>
    <link rel="stylesheet" type="text/css" href="https://cdn.c9.io/errors/style.css" />
    <style type="text/css">
    .error_content {
        background: rgba(255, 255, 255, 0.23);
        padding: 10px;
        width: 641px;
        margin: 25px 0;
        display: none;
    }

    #error-msg {
        display: block;
    }
    </style>
  </head>
  <body class="errorUnknown light">
    <div id="wrapper">
      <h1>Error 502 - Bad Gateway</h1>
      <div class="error_content" id="error-msg">
          <p>Please click <a href="javascript:location.reload(true)">here</a> to try again, if the issue persists please contact <a href="https://c9.io/support">support</a></p>
      </div>

      <a href="http://status.c9.io">Status Page</a> |
      <a href="https://c9.io/support">Support</a> |
      <a href="https://c9.io/dashboard.html">Dashboard</a> |
      <a href="https://c9.io">Home</a>
    </div>
  </body>

Answer 1

我没有足够的声誉来发表评论，但我相信当您在控制台日志中返回2个ID时发生错误。 502错误表示您不介意为用户发布您的架构，因为从那里2个ID正在以某种方式返回。

编辑：2 我想我可能已经找到了您的问题（不确定），但是在预钩中间件中

CommentSchema.pre('findOne', function(next) {
 this.populate('author');
      next();
});

此处您使用的是 findOne ，但在途中您使用的是 find 方法，这就是为什么它没有填充您的用户ID并返回 null 的原因。这是更新的版本。请尝试

router.get("/users/:id", function(req, res) {


 User.findById(req.params.id, function(err, foundUser) {
if(err) {
  req.flash("error", "Something went wrong.");
  res.redirect("/");
}
if (foundUser) {
Comment.findOne().where('author').equals(foundUser._id).exec(function(err, comments) {
  if(err) {
    req.flash("error", "Something went wrong.");
    res.redirect("/");
  }
    res.render("show", {user: foundUser, comments: comments});
  });
}
if(!foundUser){req.flash("error","User Not Found")}

让我知道是否可以解决您的错误

Answer 2

基于Shivam的评论，我将代码更新为：

if (foundUser) {
    Comment.find().where('author').equals(foundUser._id).exec(function(err, comments) {
      if(err) {
        req.flash("error", "Something went wrong.");
        res.redirect("/");
      }
        res.render("show", {user: foundUser, comments: comments});
      });
    }
    });
  });

这有效。谢谢大家的帮助

TypeError：无法读取null的属性“ _id”，仅在生产环境中无法开发

2 个答案: