[Django]-Django Admin linking to related objects

Modifying your model isn’t necessary, and it’s actually a bad practice (adding admin-specific view-logic into your models? Yuck!) It may not even be possible in some scenarios.

Luckily, it can all be achieved from the ModelAdmin class:

from django.urls import reverse
from django.utils.safestring import mark_safe    


class PageAdmin(admin.ModelAdmin):
    # Add it to the list view:
    list_display = ('name', 'user_link', )
    # Add it to the details view:
    readonly_fields = ('user_link',)

    def user_link(self, obj):
        return mark_safe('<a href="{}">{}</a>'.format(
            reverse("admin:auth_user_change", args=(obj.user.pk,)),
            obj.user.email
        ))
    user_link.short_description = 'user'


admin.site.register(Page, PageAdmin)

Edit 2016-01-17:
Updated answer to use make_safe, since allow_tags is now deprecated.

Edit 2019-06-14:
Updated answer to use django.urls, since as of Django 1.10 django.core.urls has been deprecated.

You need to use format_html for modern versions of django

@admin.register(models.Foo)
class FooAdmin(admin.ModelAdmin):
    list_display = ('ts', 'bar_link',)

    def bar_link(self, item):
        from django.shortcuts import resolve_url
        from django.contrib.admin.templatetags.admin_urls import admin_urlname
        url = resolve_url(admin_urlname(models.Bar._meta, 'change'), item.bar.id)
        return format_html(
            '<a href="{url}">{name}</a>'.format(url=url, name=str(item.bar))
        )

I ended up with a simple helper:

from django.shortcuts import resolve_url
from django.utils.safestring import SafeText
from django.contrib.admin.templatetags.admin_urls import admin_urlname
from django.utils.html import format_html


def model_admin_url(obj: Model, name: str = None) -> str:
    url = resolve_url(admin_urlname(obj._meta, SafeText("change")), obj.pk)
    return format_html('<a href="{}">{}</a>', url, name or str(obj))

Then you can use the helper in your model-admin:

class MyAdmin(admin.ModelAdmin):
    readonly_field = ["my_link"]

    def my_link(self, obj):
        return model_admin_url(obj.my_foreign_key)

I needed this for a lot of my admin pages, so I created a mixin for it that handles different use cases:

pip install django-admin-relation-links

Then:

from django.contrib import admin
from django_admin_relation_links import AdminChangeLinksMixin


@admin.register(Group)
class MyModelAdmin(AdminChangeLinksMixin, admin.ModelAdmin):

    # ...

    change_links = ['field_name']

See the GitHub page for more info. Try it out and let me know how it works out!

https://github.com/gitaarik/django-admin-relation-links

I decided to make a simple admin mixin that looks like this (see docstring for usage):

from django.contrib.contenttypes.models import ContentType
from django.utils.html import format_html
from rest_framework.reverse import reverse


class RelatedObjectLinkMixin(object):
    """    
    Generate links to related links. Add this mixin to a Django admin model. Add a 'link_fields' attribute to the admin
    containing a list of related model fields and then add the attribute name with a '_link' suffix to the
    list_display attribute. For Example a Student model with a 'teacher' attribute would have an Admin class like this:

    class StudentAdmin(RelatedObjectLinkMixin, ...):
        link_fields = ['teacher']

        list_display = [
            ...
            'teacher_link'
            ...
        ]
    """

    link_fields = []

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        if self.link_fields:
            for field_name in self.link_fields:
                func_name = field_name + '_link'
                setattr(self, func_name, self._generate_link_func(field_name))

    def _generate_link_func(self, field_name):
        def _func(obj, *args, **kwargs):
            related_obj = getattr(obj, field_name)
            if related_obj:
                content_type = ContentType.objects.get_for_model(related_obj.__class__)
                url_name = 'admin:%s_%s_change' % (content_type.app_label, content_type.model)
                url = reverse(url_name, args=[related_obj.pk])
                return format_html('<a href="{}" class="changelink">{}</a>', url, str(related_obj))
            else:
                return None
        return _func

If anyone is trying to do this with inline admin, consider a property called show_change_link since Django 1.8.

Your code could then look like this:

class QuestionInline(admin.TabularInline):
    model = Question
    extra = 1
    show_change_link = True


class TestAdmin(admin.ModelAdmin):
    inlines = (QuestionInline,)


admin.site.register(Test, TestAdmin)

This will add a change/update link for each foreign key relationship in the admin’s inline section.