Mongoose TypeError on a model's findOne method

Question

The following TypeError cropped up in some old code.

TypeError: Object #<Object> has no method 'findOne'

The Model that was affected recently had two new static methods defined and those methods referenced external models. After backing out the new static methods, I was able to determine the root cause to be the require statements of the external models. The pattern looks like the following:

var UserModel = require('./user');

var GroupSchema = new Schema({
    name: String,
    users: [{ type : Schema.ObjectId, ref: 'UserModel'}],
});

GroupSchema.statics.findSomeUsers = function(group, callback) {
    this.find({name : session_user._id}, function(err, groups) {
        UserModel.find({_id : {$in : group.users}}, function(err,patients) {
            // do magic
        });
    });
};

module.exports = mongoose.model('GroupModel', GroupSchema);

There is a code fragment in the application that calls GroupModel.findOne({name:'gogo'}) that leads to the TypeError. when I remove the require statement for the UserModel in the GroupSchema, app code works again.

Why does Javascript start to think findOne() is an instance method with the addition of the require statement?

Answer 1

It's known node.js issue. It means that you have looping require somewhere in your code and node.js forbids it.

The right way to do it is by using mongoose.model method. So, instead of UserModel variable you shall use mongoose.model('UserModel'). So, when findSomeUsers will be called mondoose will fetch UserModel and invoke its find method.

GroupSchema.statics.findSomeUsers = function(group, callback) {
    this.find({name : session_user._id}, function(err, groups) {
        mongoose.model('UserModel').find({_id : {$in : group.users}}, function(err,patients) {
            // do magic
        });
    });
};