如何将依赖项从一个应用程序注入到另一个应用程序的 Django 类中？

Question

Is there a clean method to inject dependencies from one Django app into another?

I have multiple Django apps with one of them being a base app. This means, that the other apps depend on it,but the base app should not be aware of the other apps. In most cases this is not a problem with the dependents using ForeignKeys and ManyToMany relations to the models of the base app. However, when building the admin classes, in order to add inlines and links to the respective dependent class,it is necessary to specify this in the base app. Is it possible to inject it directly from the dependent app?

Answer 1

In addition to the answer for adding inlines , I had to add attributes to the class for the list disply and list filter. Below is the code to add this for one ForeignKey linked model. Foo is a parent model (in the sense of composition over inheritance ) to which several other child models link to via OneToOne or ForeignKey fields from other apps. This ensures that the parent model and thereby the app in which it resides does not have any dependencies on its child models.

Models and admin classes defined in the parent App A.

# app_a/models.py
from django.db import models

class Foo(models.Model):
    name = models.CharField(max_length=64)

# app_a/admin.py
from django.contrib import admin
from .models import Foo

@admin.register(Foo)
class FooAdmin(admin.ModelAdmin):
    list_display = ["name"]
    list_display_links = ("name",)
    list_filter = []
    list_select_related = []

Models and admin classes defined in the child App B.

# app_b/models.py
from django.db import models
from app_a.models import Foo

class BarComponent(models.Model):
    foo = models.OneToOneField(
        Foo,
        primary_key=True,
        related_name="bar_component",
        on_delete=models.CASCADE,
    )
    bar_type = models.CharField(max_length=42)

# app_b/admin.py
from django.contrib import admin
from django.core.exceptions import ObjectDoesNotExist

from .models import BarComponent
from app_a.admin import FooAdmin

@admin.register(BarComponent)
class BarAdmin(admin.ModelAdmin):
    pass

# Inject BarComponent aspect into admin for Foo
@mark_safe
def has_bar(self, obj):
    try:
        return '<a href="%s">%s</a>' % (
            reverse(
                "admin:appb_barcomponent_change",
                args=(obj.bar_component.pk,),
            ),
            obj.bar_component.bar_type,
        )
    except ObjectDoesNotExist:
        return "-"


setattr(FooAdmin, "has_bar", has_bar)
setattr(FooAdmin.has_bar, "allow_tags", True)
setattr(FooAdmin.has_bar, "short_description", "Bar")
FooAdmin.list_display.append("has_bar")
FooAdmin.list_filter.append(("bar_component", admin.EmptyFieldListFilter))
FooAdmin.list_select_related.append("bar_component")

Disclaimer: The code was foobar'ed from functional code in my project. Therefore, it has not been tested, but the structure works my project .