Question

我的模型看起来像这样：

mongoose.Schema({
  username: String,
  posts: [{ type: Schema.Types.ObjectId, ref: 'Post' }]
});

我有一个端点，我想传递一个ObjectID：

app.delete('/post', function(req, res) {
  User.findOne({ _id: req.user._id}, function(err, result) {
    result.pull({ _id: req.body.post_id });
  });
});

感觉它应该有效，但我收到了这个错误：

CastError: Cast to ObjectId failed for value "[object Object]"

我做错了什么？

Answer 1

如果要从数组中删除一个元素，请使用此

User
.update( 
  {_id: req.user._id}, 
  { $pull: {posts: req.body.post_id } } 
)
.then( err => {
  ...
});

这里是documentation

Answer 2

This is because when you are running user findOne query it returns an object to you.(the findOne function returns only one object)

User.findOne({ _id: req.user._id}, function(err, result) {

 /// result is an object
    result.pull({ _id: req.body.post_id });
  });

and what is result.pull you are trying to pull an element from object this is the wrong way to do

do like this 
delete result._id;


and if you want more elements from user query in from of array you can use 
User.find({ _id: req.user._id}, function(err, result) {

// result.slice for slice you can see this http://stackoverflow.com/questions/3396088/how-do-i-remove-an-object-from-an-array-with-javascript
  });

then you can do slice on array of object

Answer 3

为了在集合中使用id进行研究，您需要创建一个新的ObjectId，然后将id传递给它。

adb shell am start -n com.mediatek.camera/com.android.camera.CameraActivity

Mongoose：根据ID（Cast Error）从数组中删除对象

3 个答案: