How can I define a list field in django rest framework?

Question

Let's say I have a class

class Tags(object):

    tags = []

    def __init__(self, tags):
        self.tags = tags

and a custom list field

class TagsField(serializers.WritableField):
    """
    Returns a list of tags, or serializes a list of tags
    """

I am not too sure where to go from here. How can I make sure that a blog post serializer defined as

class BlogPostSerializer(serializers.Serializer):
    post = CharField()
    tags = TagsField

would give me a json object similar to

{
    "post": "Here is my blog post about python",
    "tags": ["python", "django", "rest"]
}

Answer 1

There is also the ListField in django rest framework, see http://www.django-rest-framework.org/api-guide/fields/#listfield

wtih the examples:

scores = serializers.ListField(
    child=serializers.IntegerField(min_value=0, max_value=100)
)

and (other notation):

class StringListField(serializers.ListField):
    child = serializers.CharField()

this seems simpler (maybe this class is added later than the accepted anwser, but seems good to add this option anyway)

By the way, it's added since djang rest framework 3.0: http://www.django-rest-framework.org/topics/3.0-announcement/

Answer 2

One way to deal with arrays for a non ORM-based object is to override the to_native and from_native methods. In your case:

class TagsField(serializers.WritableField):

    def from_native(self, data):
        if isinstance(data, list):
            return Tags(data)
        else:
            msg = self.error_messages['invalid']
            raise ValidationError(msg)

    def to_native(self, obj):
        return obj.tags

If you had an ORM-based object you would like to look at the SlugRelatedField with the many = True attribute.

---

From Django Rest Framework version 3.0 you can also use ListField http://www.django-rest-framework.org/api-guide/fields/#listfield