How to make only the 1st inline object boolean field "True" by default only for "Add" page in Django Admin?

Question

I'm trying to make only the 1st inline object boolean field True by default only for Add page.

So, I have Person model and Email model which has the foreign key of Person model as shown below:

# "models.py"

class Person(models.Model):
    name = models.CharField(max_length=20)

    def __str__(self):
        return self.name

class Email(models.Model):
    person = models.ForeignKey(Person, on_delete=models.CASCADE)
    is_used = models.BooleanField()
    email = models.EmailField()

    def __str__(self):
        return self.email

Then, I set the custom form EmailForm to form in EmailInline() as shown below:

# "admin.py"

class EmailForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        kwargs['initial'] = {'is_used': True}
        super().__init__(*args, **kwargs)

class EmailInline(admin.TabularInline):
    model = Email
    form = EmailForm # Here
    
@admin.register(Person)
class PersonAdmin(admin.ModelAdmin):
    inlines = (EmailInline,)

But, all inline objects are is_used=True by default on Add page as shown below:

And, I added one main object with one inline object which is is_used=True as shown below:

But, the added inline object and other not-yet-added inline objects are is_used=True on Change page as shown below:

And, I added one main object with one inline object which is is_used=False as shown below:

But, the added inline object and other not-yet-added inline objects are is_used=True on Change page as shown below:

So, how can I make only the 1st inline object boolean field True by default only for Add page?

Does this answer your question? [Django: Admin inline forms initial data for every instance](https://stackoverflow.com/questions/12384973/django-admin-inline-forms-initial-data-for-every-instance) — Abdul Aziz Barkat, May 17 '23 at 14:28

score 0 · Answer 1 · answered May 17 '23 at 01:08

You can use the global variable count in __init__() and overridden get_formset() and set EmailForm to self.form in overridden get_formset() as shown below to make only the 1st inline object boolean field True by default only for Add page:

# "admin.py"

count = 0 # Here
class EmailForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        global count
        if count < 1:
            kwargs['initial'] = {'is_used': True}
            count += 1
        super().__init__(*args, **kwargs)

class EmailInline(admin.TabularInline):
    model = Email
    
    def get_formset(self, request, obj=None, **kwargs):
        if not obj:
            self.form = EmailForm
        global count
        count = 0
        return super().get_formset(request, obj, **kwargs)

@admin.register(Person)
class PersonAdmin(admin.ModelAdmin):
    inlines = (EmailInline,)

Then, only the 1st inline object is is_used=True by default on Add page as shown below:

And, I added one main object with one inline object which is is_used=True as shown below:

Then, only the added inline object is is_used=True on Change page as shown below:

And, I added one main object with one inline object which is is_used=False as shown below:

Then, the added inline object and other not-yet-added inline objects are is_used=False on Change page as shown below:

In addition, if changing count < 1 to count < 2 as shown below:

# "admin.py"

count = 0
class EmailForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        global count
        if count < 2: # Here
            kwargs['initial'] = {'is_used': True}
            count += 1
        super().__init__(*args, **kwargs)

# ...

Then, the 1st and 2nd inline objects are is_used=True by default on Add page as shown below:

@Abdul Aziz Barkat Because of it uses the global variable `count`? — Super Kai - Kazuya Ito, May 17 '23 at 14:36
Yes, assume two (or more) users make a request at about the same time. One possibility is the reset to 0 causes other users to have multiple `True` defaults, while another possibility is that a user never gets a `True` default since the other user already caused the `count` to increment. Global variables are quite prone to race conditions. — Abdul Aziz Barkat, May 17 '23 at 14:40

How to make only the 1st inline object boolean field "True" by default only for "Add" page in Django Admin?

1 Answers1