Mongoose auto increment

According to this mongodb article it is possible to auto increment a field and I would like the use the counters collection way.

The problem with that example is that I don’t have thousands of people typing the data in the database using the mongo console. Instead I am trying to use mongoose.

So my schema looks something like this:

var entitySchema = mongoose.Schema({
  testvalue:{type:String,default:function getNextSequence() {
        console.log('what is this:',mongoose);//this is mongoose
        var ret = db.counters.findAndModify({
                 query: { _id:'entityId' },
                 update: { $inc: { seq: 1 } },
                 new: true
               }
        );
        return ret.seq;
      }
    }
});

I have created the counters collection in the same database and added a page with the _id of ‘entityId’. From here I am not sure how to use mongoose to update that page and get the incrementing number.

There is no schema for counters and I would like it to stay that way because this is not really an entity used by the application. It should only be used in the schema(s) to auto increment fields.

Answer

Here is an example how you can implement auto-increment field in Mongoose:

var CounterSchema = Schema({
    _id: {type: String, required: true},
    seq: { type: Number, default: 0 }
});
var counter = mongoose.model('counter', CounterSchema);

var entitySchema = mongoose.Schema({
    testvalue: {type: String}
});

entitySchema.pre('save', function(next) {
    var doc = this;
    counter.findByIdAndUpdate({_id: 'entityId'}, {$inc: { seq: 1} }, function(error, counter)   {
        if(error)
            return next(error);
        doc.testvalue = counter.seq;
        next();
    });
});