[FIXED] How to modify values in m2m field in form? (Django)

Issue

I have 2 models in my models.py. They are Doctor and Specialty:

class Doctor(models.Model):
    name = CharField(max_length=255)
    specialties = ManyToManyField('Specialty', related_name='doctors')
    mc_id = CharField(max_length=255, unique=True)

class Specialty(models.Model):
    name = CharField(max_length=255)
    mc_id = CharField(max_length=255, unique=True)

    def __str__(self):
        return self.name

When i'm creating new Doctor instance via admin interface (change_form.html template) I see my Doctor model fields, which I should fill with data. Among these fields there is a field specialties ("Cпециальности"), which is m2m field and contains names (as I set __str__(self) method in Specialty model to return self.name) for specialties which were previously added to Specialty model (see a screen).

All I want is to see in this list not only specialty names, but also values of mc_id field of Specialty model, but it is not my case to make it at the expense of something like this:

class Specialty(models.Model):
    name = CharField(max_length=255)
    mc_id = CharField(max_length=255, unique=True)

    def __str__(self):
        return self.name + '(' + self.mc_id + ')'

I thought i could make it through overriding of formfield_for_manytomany() method in my admin model (associated with Doctor model) in admin.py:

@admin.register(Doctor)
class DoctorAdmin(admin.ModelAdmin):
    def formfield_for_manytomany(self, db_field, request, **kwargs):
        if db_field.name == "specialties":
            queryset = Specialty.objects.all()
            for specialty in queryset:
                specialty.name += '(' + {specialty.mc_id} + ')'
        return super().formfield_for_manytomany(db_field, request, **kwargs)

It didn't work. I'd like to know how can i solve my problem. Thank you in advance.

UPDATE: I'd also like to make a content of specialties field in the form user-dependent:

• if superuser tries to add new doctor he will see in the specialties field of the form values like:
  • Internal Medicine (mc1_id)
  • Neurology (mc1_id)
  • Cardiology (mc2_id)
• if normal user which name is 'mc1_id' tries to add new doctor he will see in the form values filtered by his name and without '(mc_id)'-part. Like:
  • Internal Medicine
  • Neurology

Solution

I think that overwrite the label_from_instance method in the form field can work for you.

class SpecialtyModelMultipleChoiceField(forms.ModelMultipleChoiceField):

    def label_from_instance(self, obj):
        obj.name + '(' + obj.mc_id + ')'


class DoctorModelForm(forms.ModelForm):
    specialties = SpecialtyModelMultipleChoiceField(
        Specialty.objecs.all
        # ....
    )
    
    class Meta:
        model = Doctor
        fields = '__all__'


@admin.register(Doctor)
class DoctorAdmin(admin.ModelAdmin):
    form = DoctorModelForm
    # ....

UPDATE:

In order to make the field text user dependent you can return different classes in the get_form method of the Admin Model:

class SpecialtyModelMultipleChoiceField(forms.ModelMultipleChoiceField):

    def label_from_instance(self, obj):
        obj.name + '(' + obj.mc_id + ')'


class DoctorModelForm(forms.ModelForm):
    specialties = SpecialtyModelMultipleChoiceField(
        Specialty.objecs.all
        # ....
    )
    
    class Meta:
        model = Doctor
        fields = '__all__'


class SimpleDoctorModelForm(forms.ModelForm):
    
    class Meta:
        model = Doctor
        fields = '__all__'


@admin.register(Doctor)
class DoctorAdmin(admin.ModelAdmin):
    
    def get_form(self, request, obj=None, **kw):
        if request.user.is_superuser:
            return DoctorModelForm
        return SimpleDoctorModelForm

If you need more, you can set properties in the form and work with its in the constructor:

class DoctorModelForm(forms.ModelForm):
    
    class Meta:
        model = Doctor
        fields = '__all__'

    @classmethod
    def set_user(cls, user):
        cls.__user = user

    def __init__(self, *args, **kw):
        super(DoctorModelForm, self).__init__(*args, **kw)
        if self.__user.condition:
            self.fields['specialties'] = MyCustomField


@admin.register(Doctor)
class DoctorAdmin(admin.ModelAdmin):
    form = DoctorModelForm

    def get_form(self, request, obj=None, **kw):        
        form_class = super(DoctorAdmin, self).get_form(request, obj, **kw)
        form_class.set_user(request.user)

        return form_class

Answered By - Tonio