Mongoengine: How to get one specific embedded document?

Question

How can I get one specific embedded document eg by ID with mongoengine?

These are my models:

class Project(Document):
    project_name = StringField(unique=True, required=True)
    literature = ListField(EmbeddedDocumentField(Literature))

class Literature(EmbeddedDocument):
    id = ObjectIdField(required=True, default=ObjectId,
                        unique=True, primary_key=True, sparse=True)
    title = StringField()

and I want to get a specific Literature Object eg by the id "2".

I tried this:

literature = Project.objects(project_name=project_name).get(
        literature__id=2).literature

but this gives me all literature objects and not only the one with the ID "2"

I've also tried something like this:

literature = Project.objects.get(project_name=project_name).literature.filter(
        literature__id=2)

but this throws the error AttributeError: 'BaseList' object has no attribute 'filter'

so is there any way to get only that specific embedded document (literature with the ID= 2)? Dont know what else I could do

Cheers

Answer 1

When you are doing query, it will still point to specific Project document with liteature__id mentioned. You have to use filter for the query.

literature = Project.objects.filter(project_name=project_name,literature__id=id)

This will still point to Project object since you are doing query on Project and Literature is an embedded document inside it.