如何使用 mongoose 添加到这个架构数组？

Question

Here's the user schema and the part I want to update is ToDo under User.js (further down). I am attempting to add new data to an array within the db.

data.js

app.post("/data", loggedIn, async (req, res) => {
  console.log(req.body.content);
  let content = { content: req.body.content };
  User.update({ _id: req.user._id }, { $set: req.body }, function (err, user) {
    if (err) console.log(err);
    if (!content) {
      req.flash("error", "One or more fields are empty");
      return res.redirect("/");
    }
    user.ToDo.push(content);
    res.redirect("/main");
  });
});

User.js

  new mongoose.Schema({
    email: String,
    passwordHash: String,
    ToDo: {
      type: [],
    },
    date: {
      type: Date,
      default: Date.now,
    },
  })

Originally I was trying the .push() attribute, but I get the error:

 user.ToDo.push(content); ^

TypeError: Cannot read property 'push' of undefined

Answer 1

First of all, your problem is the callback is not the user. When you use update the callback is something like this:

{ n: 1, nModified: 1, ok: 1 }

This is why the error is thrown.

Also I recommend specify the array value, something like this:

ToDo: {
  type: [String],
}

The second recommendation is to do all you can into mongo query. If you can use a query to push the object, do this instead of store the object into memory, push using JS function and save again the object into DB.

Of course you can do that, but I think is worse.

Now, knowing this, if you only want to add a value into an array, try this query:

var update = await model.updateOne({
  "email": "email"
},
{
  "$push": {
    "ToDo": "new value"
  }
})

Check the example here

You are using $set to your object, so you are creating a new object with new values.

Check here how $set works.

If fields no exists, will be added, otherwise are updated. If you only want to add an element into an array from a specified field, you should $push into the field.

Following your code, maybe you wanted to do something similar to this:

model.findOne({ "email": "email" }, async function (err, user) {
  //Here, user is the object user
  user.ToDo.push("value")
  user.save()
})

As I said before, that works, but is better do in a query.