remove nested object references mongoose - mongodb

Question

I have several mongoose models in my application - assignment, submisssion, and file.
var assignmentSchema = new Schema({
submissions:[{
type: mongoose.Schema.Types.ObjectId,
ref: 'Submission'
}]
});
var submissionSchema = new Schema({
assignment: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Assignment'
},
files: [{
type: mongoose.Schema.Types.ObjectId,
ref: 'File'
}],
})
var fileSchema = new Schema({
submission: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Submission'
}
})
I defined a remove hook for assignments, so when an assignment is removed from my mongodb, all submissions are deleted too.
assignmentSchema.pre('remove', function (next) {
var assignment = this;
assignment.model('Class').update(
{_id: {$in: assignment.classes}},
{$pull: {assignments: assignment._id}},
{multi: true},
next
);
//will delete all submissions that were in the assignment
assignment.model('Submission').remove(
{_id: {$in: assignment.submissions}}).exec();
next
});
It works ok, but I also want to remove all files that are related to deleted submissions. How can I achieve this?

Answer 1

You have to setup a pre remove hook for your submission documents.
Then in your assignmentSchema loop through the assignment.submissions array, find each assignment document and execute a remove on that document.
Here is an example. Not tested.
assignmentSchema.pre('remove', function(nextAction) {
var assignment = this;
assignment.model('Class').update({
_id: {
$in: assignment.classes
}
}, {
$pull: {
assignments: assignment._id
}
}, {
multi: true
},
next
);
Async.each(assignment.submissions, function(subId, next) {
submissionSchema.findById(subId).exec(function(err, submission) {
submission.remove();
next();
})
}, function() {
nextAction();
})
});
submissionSchema.pre('remove', function (next) {
///remove files here.
})