Support object polymorphism

[abendebury]

In my application, I have an API endpoint like so:

/api/activities/

In my database, I have several different types of Activity models, all inheriting from a common class. I made a schema like so:

class ActivitySchema(ModelSchema):
    class Meta:
        model = models.Activity

And then have flask-restful handle the api endpoint itself, querying the database and passing the objects to marshmallow-alchemy.

However, marshmallow-sqlalchemy serializes the objects as if they were all of the base Activity type. It would be nice if there was some support like this:

class ActivitySchema(ModelSchema):
    class Meta:
        model = models.Activity
        generate_polymorphic_schemas = True

Which would use sqlalchemy's inspection to view all polymorpic subclasses of Meta.model, store them on ActivitySchema, and then when serializing/deserializing use the appropriate class.

Thoughts?

If this is a desirable feature, I can try to make a PR implementing such functionality.

[dolfandringa]

@abendebury: any chance that you got to do that PR?

[abendebury]

Sorry, I have not been able to do so.

[sloria]

Sorry for the long delay, but I recommend using https://github.com/marshmallow-code/marshmallow-oneofschema for this. It works well for serializing based on a discriminator column.