Accessing a proxy model from the parent within a template

Question

I have the following Django model that extends the Post model from django basic blog:

from django.basic.blog.models import Post
from l10n.utils import lookup_translation

class ExtendedPost(Post):
    class Meta:
        proxy = True
    def translated_title(self, language_code=None):
        return lookup_translation(self, 'title', language_code)

I'm trying to use django basic blog's view by just overriding their template and making use of the new ExtendedPost behaviour in there:

{{ post.extendedpost.translated_title }}

But obviously this doesn't work because you can't just access a subclass like that. How DO you do this type of thing?

score 1 · Accepted Answer · edited May 23 '17 at 10:33

Well, the view would still be referencing the original model, so you'd have to modify the view to pass in the ExtendedPost class.

You can't just define a proxy model and have it magically override the parent class.

Untested idea based on: Can django's auth_user.username be varchar(75)? How could that be done?

from django.db.models.signals import class_prepared

def add_func(sender, *args, **kwargs):
    if sender.__name__ == "Post" and sender.__module__ == "django-basic-blog-module":
        sender.translated_title = lambda self, language_code=None: lookup_translations(self, 'title', language_code)

class_prepared.connect(add_func)

Override sys.modules

import sys
from django.basic.blog import models

models.Post.translated_title = lambda self, language_code=None: lookup_translations(self, 'title', language_code)

Is there a way to modify (reuse) the view without redefining it in my own code? I still want to pick up changes to the django-basic-blog app later on, and don't want to have to merge those changes every time I do. — pancakes, Feb 27 '11 at 05:37

score 0 · Answer 2 · answered Feb 27 '11 at 05:31

0

You can make

{{ post.extendedpost.translated_title }}

work if you use multi-table inheritance rather than a proxy model.

However, introducing a whole new table just to add a function doesn't make a whole lot of sense.

answered Feb 27 '11 at 05:31

pancakes

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score 0 · Answer 3 · answered Jun 09 '22 at 18:07

This issue is too old but I found a solution that works for me and I will share it

you can just create a decorator like this:

def connect_proxy_to_model(property_name=None, return_copy=False):
    def get_proxy_func(proxy_class, self):
        if return_copy:
            proxy_obj = copy.deepcopy(self)
        else:
            proxy_obj = self
        proxy_obj.__class__ = proxy_class
        return proxy_obj

    def connect(proxy_class):
        name = property_name if property_name else proxy_class.__name__.lower()
        setattr(proxy_class.__base__, name, property(lambda self: get_proxy_func(proxy_class, self)))

    def wrapper(proxy_class):
        connect(proxy_class)
        return proxy_class

    return wrapper

And then you can decorate your proxy model with this:

from django.basic.blog.models import Post
from l10n.utils import lookup_translation


@connect_proxy_to_model(property_name='extendedpost', return_copy=True)
class ExtendedPost(Post):
    class Meta:
        proxy = True

    def translated_title(self, language_code=None):
        return lookup_translation(self, 'title', language_code)

Now you can use it just doing

{{ post.extendedpost.translated_title }}

The return_copy option that helps you if you want overwrite the current object ty

Accessing a proxy model from the parent within a template

3 Answers3