Access to marshmallow field value

Question

I begin with marshamallow and I try to validate a field. My schema is very simple.

class MySchema(Schema):
    pid = fields.String(required=true)
    visibility = fields.String(validate=OneOf(['public','private'])

    @validates('visibility')
    def visibility_changes(self, data, **kwargs):
        # Load data from DB (based on ID)
        db_record = load_data_from_db(self.pid)  # <-- problem is here
        # Check visibility changed
        if db_record.get('visibility') != data:
            do_some_check_here()

But using self.pid doesn't work. It raises an error AttributeError: 'MySchema' object has no attribute 'pid'. What's the correct way to access to my "pid" field value into my @validates function ?

I tried using self.fields, self.load_fields.get('pid').get_value(), ... no easy way to access it, but I suppose that Marshmallow has such magic method.

Thanks for your help.

Answer 1

You should use @validates_schema to define a validator that works on several fields. It takes the whole input payload as argument so you can find pid in there.