Adding client side calculated fields to django admin

Question

Say I've got a model like so:

class Spam(models.Model):
    a = models.IntegerField()
    b = models.IntegerField()

On the admin create/edit form. I want to add a non-editable field "c", that will contain the sum of whatever has been entered in a and b.

I have a boatload of ideas on how to accomplish this, and none of them sound very good.

Can anyone point me in the right direction?

Answer 1

You can do it with ModelAdmin.readonly_fields

class SpamAdmin(admin.ModelAdmin):
    readonly_fields = ('get_c',)
    fields = ('a', 'b', 'get_c')

    def get_c(self, obj):
        return obj.a + obj.b