来自Foreignkey的字段未在django admin中显示数据

Question

I am trying to show fields from foreignkey, So my fields are showing but with empty value, i have value for these field. I have following code for

admin.py

@admin.register(OrderDetail)
class OrderDetailAdmin(admin.ModelAdmin):
    list_select_related = ('category', 'industry', 'user')
    fieldsets = (
        ('User Information', {'fields': ('first_name', 'last_name', 'email',),}),
    )
    readonly_fields = ('first_name', 'last_name', 'email',)

    def first_name(self, obj):
        obj.user.first_name

    first_name.short_description = 'First Name'

    def last_name(self, obj):
        obj.user.last_name

    def email(self, obj):
        obj.user.email

and related model code is here:

class OrderDetail(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)

Answer 1

You did not return anything from these functions:

def last_name(self, obj):
    return obj.user.last_name