Populate mongoose array of objects
It wont work as system is not a property of systems. You need to populate it like
Module.findOne({project: pId}).sort('-created') .populate('systems.0.system').exec(function (err, doc){})Module.findOne({project: pId}).sort('-created') .populate('systems.1.system').exec(function (err, doc){})So you should have a for loop and iterate over it to populate all the documents. Else you should modify your model to make it work better.
var ModuleSchema = new Schema({systems: [{ system: { type: Schema.ObjectId, ref: 'System' }, quantity: { type: Number } }]});Change your model to this and it will make easy for you.
var ModuleSchema = new Schema({ systems: { system: [{ type: Schema.ObjectId, ref: 'System' }], quantity: { type: Number } } });