Link To Foreignkey in Admin Causes AttributeError When Debug Is False

Question

I have used the following code in my models.py file:

Create hyperlink to foreignkey

class ModelAdminWithForeignKeyLinksMetaclass(MediaDefiningClass): 
         


        

Answer 1

I uses stepank's implementation, but had to alter it slightly to fit my use-case.

I basically just added support for 'ModelAdmin.readonly_fields' and 'ModelAdmin.fields' to support the 'link_to_'-syntax.

A slight change to the link creation also allowed me to support a link to a different APP.Model, in my case the built-in django.contrib.auth.models.user.

Thanks for the nice work @stepank and @Itai Tavor.

I hope this is useful for somebody else.

---

DEFAULT_LOGGER_NAME is defined in my settings.py and I use it for most of my logging. If you don't have it defined, you will get errors when using the following code. You can either define your own DEFAULT_LOGGER_NAME in settings.py (it is just a simple string) or you just remove all references to the logger in the code below.

'''
Created on Feb 23, 2012

@author: daniel

Purpose: Provides a 'link_to_' function for ModelAdmin 
         implementations. This is based on the following work:

original: http://stackoverflow.com/a/3157065/193165
fixed original: http://stackoverflow.com/a/7192721/193165
'''
from functools      import partial
from django.forms   import MediaDefiningClass

import logging
from public.settings import DEFAULT_LOGGER_NAME
logger = logging.getLogger(DEFAULT_LOGGER_NAME)

class ForeignKeyLinksMetaclass(MediaDefiningClass):

    def __new__(cls, name, bases, attrs):

        new_class = super(
            ForeignKeyLinksMetaclass, cls).__new__(cls, name, bases, attrs)

        def foreign_key_link(instance, field):
            target = getattr(instance, field)
            ret_url = u'%s' % (
                      target._meta.app_label, target._meta.module_name,
                      target.id, unicode(target)
                      ) 
            #I don't know how to dynamically determine in what APP we currently
            #are, so this is a bit of a hack to enable links to the 
            #django.contrib.auth.models.user
            if "auth" in target._meta.app_label and "user" in target._meta.module_name:
                ret_url = u'%s' % (
                          target._meta.app_label, target._meta.module_name,
                          target.id, unicode(target)
                          )                    
            return ret_url

        def _add_method(name):
            if name is None: return
            if isinstance(name, basestring) and name[:8] == 'link_to_':
                try:
                    method = partial(foreign_key_link, field=name[8:])
                    method.__name__ = name[8:]
                    method.allow_tags = True
                    #in my app the "user" field always points to django.contrib.auth.models.user
                    #and I want my users to see that when they edit "client" data
                    #"Client" is another model, that has a 1:1 relationship with 
                    #django.contrib.auth.models.user
                    if "user" in name[8:]: 
                        method.short_description = "Auth User"
                    setattr(new_class, name, method)
                except Exception, ex:
                    logger.debug("_add_method(%s) failed: %s" % (name, ex))
        #make this work for InlineModelAdmin classes as well, who do not have a
        #.list_display attribute
        if hasattr(new_class, "list_display") and not new_class.list_display is None:
            for name in new_class.list_display:
                _add_method(name)
        #enable the 'link_to_' syntax for the ModelAdmin.readonly_fields
        if not new_class.readonly_fields is None:
            for name in new_class.readonly_fields:
                _add_method(name)
        #enable the 'link_to_' syntax for the ModelAdmin.fields
        if not new_class.fields is None:
            for name in new_class.fields:
                _add_method(name)

        return new_class