Comment by Jaco Vinus on "“UnhandledPromiseRejectionWarning: CastError: Cast to ObjectId failed for value”"

meetups: [{ type: Schema.Types.ObjectId, ref: 'Meetup', }],

better try with:

meetups: { type: Schema.ObjectId, ref: 'Meetup' }

and declare : const Schema = mongoose.Schema; (it will be the Schema inside the type: -Schema -)

before: const GroupSchema = new Schema {

Try to separate the model of the functions to establish a structure finishing the module file with:

module.exports = mongoose.model('Group', groupSchema);

and then the meetup function in another file.

Hope it helps :)

Search Hashnode