停止影响 Django 多对多 model 的其他对象

Question

I'm trying to replicate Blood Group as Model as defined in this picture. .

In my models.py file I had my code to replicate the blood groups like this

class BloodGroup(models.Model):
    name = models.CharField(
        max_length=3
    )
    gives = models.ManyToManyField("self")
    receives = models.ManyToManyField("self")

    def __str__(self):
        return self.name

And in my admin.py file I had registered the model as follows

class BloodGroupAdmin(admin.ModelAdmin):
    model = BloodGroup
    list_display = ['name', 'get_gives', 'get_receives']

    def get_gives(self, obj):
        return ", ".join([item.name for item in obj.gives.all()])

    def get_receives(self, obj):
        return ", ".join([item.name for item in obj.receives.all()])

admin.site.register(BloodGroup, BloodGroupAdmin)

Initially I created plain BloodGroup objects without their gives and receives attribute by providing just their names alone. Thus I create an object for all 8 types. Then as I added relationships to each object I found that adding gives or receives for one object affects other objects gives and receives too, making it impossible to replicate the structure in image.

1. How do I define relationships, without affecting other objects?
2. In my admin site, I see field names as "get_gives" and "get_receives". How would i make the admin page show field names as "gives" and "receives" but still displaying objects as strings like the image below?

Answer 1

For first question , probably it is better to have only one relation gives . receives can be found from the reverse query . Like this:

class BloodGroup(models.Model):
    name = models.CharField(
        max_length=3
    )
    gives = models.ManyToManyField("self", related_name="receives", symmetrical=False)

Then you only need to add objects to gives . receives will be generated automatically.

For second question , add short_description attribute to function( reference to docs ). Like this:

get_gives.short_description = 'Gives'
get_receives.short_description = 'Receives'