Flask-Restplus: how to model string or object?

Question

In Flask-Restplus, I need to model an attribute value that maybe either a list of strings or a list of objects.

That is it can look like this:

{
    'my_attribute': [
         'value1',
          'value2'
     ]
}

or it can look like the following:

{
    'my_attribute': [
        {
             'name': 'value1',
              'foo': 'something'
         },
         {
              'name': 'value2',
               'foo': 'something else'
          }
     ]
}

How should I model that in Flask-Restplus’ api.model?

score 8 · Accepted Answer · edited Oct 05 '20 at 13:22

I've just figured this out myself. In short, create a custom field class that emits its own JSON schema. In turn the schema uses the oneOf type to specify that this is either a string or an object.

from flask_restplus import fields

element_object = api.model('Element_Object', {
    'name': fields.String(),
    'foo': fields.String()
})

class StringOrObjectElement(fields.Nested):
    __schema_type__ = ['string','object']

    def output(self, key, obj):
        if isinstance(obj, str):
            if key == 'name':
                return obj
            else:
                return 'default_value'
        return super().output(key, obj)

    def schema(self):
        schema_dict = super().schema()
        schema_dict.pop('type')
        nested_ref = schema_dict.pop('$ref')
        schema_dict['oneOf'] = [
            {
                'type': 'string'
            },
            {
                '$ref': nested_ref
            }
        ]
        return schema_dict

root_object = api.model('Root_Object', {
    'my_attribute': fields.List(fields.StringOrObjectElement(element_object))

Flask-Restplus: how to model string or object?

1 Answers1