Question

I have my own User model in app engine, which should have a property of his gravatar url. However, since this can be very quickly computed using his email address, it doesn’t make sense to store it. Is there a way to just automatically initialize this property when it s loaded from the datastore?

I could just add a method called get_avatar_url(), but you can’t call an object’s methods (as far as I know), from within a jinja2 template, and I don’t want to post all these values individually to the template.

Answer 1

It’s ok to call them from a template. All you need to do is to declare this model’s method as classmethod or property

Here’s a quick example:

# sample model
class UserProfile(db.Model):
    ...
    email = db.EmailProperty()
    ...

    @property
    def id(self):
        return self.key().id()

    @classmethod
    def get_avatar_url(self):
        # whatever you need to call gravatar url
        return self.email

# sample view
def show_user(user_id):
    user = User.all().filter("user = ", user_id).get()
    flowers = Flower.all().filter("user = ", user)
    return render_template('index.html', u=user, f=flowers)

# sample template
<div class="user">user id: {{ u.id }}, and gravatar: {{ u.get_gravatar_url() }}<div>

HTH.