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django admin make a field read-only when modifying obj but required when adding new obj

Posted by: admin November 30, 2017 Leave a comment

Questions:

In admin I would like to disable a field when modifying object, but make it required when adding new object.

Whats the django way to go about this one?

Answers:

You can override the admin’s get_readonly_fields method:

class MyModelAdmin(admin.ModelAdmin):

    def get_readonly_fields(self, request, obj=None):
        if obj: # editing an existing object
            return self.readonly_fields + ('field1', 'field2')
        return self.readonly_fields

Questions:
Answers:

If you want to set all fields as read only just on the change view, override the admin’s get_readonly_fields:

def get_readonly_fields(self, request, obj=None):
    if obj: # editing an existing object
        # All model fields as read_only
        return self.readonly_fields + tuple([item.name for item in obj._meta.fields])
    return self.readonly_fields

And if you want to hide save buttons on change view:

  1. Change the view

    def change_view(self, request, object_id, form_url='', extra_context=None):
        ''' customize edit form '''
        extra_context = extra_context or {}
        extra_context['show_save_and_continue'] = False
        extra_context['show_save'] = False
        extra_context['show_save_and_add_another'] = False # this not works if has_add_permision is True
        return super(TransferAdmin, self).change_view(request, object_id, extra_context=extra_context)
    
  2. Change permissions if user is trying to edit:

    def has_add_permission(self, request, obj=None):
       # Not too much elegant but works to hide show_save_and_add_another button
        if '/change/' in str(request):
            return False
        return True
    

    This solution has been tested over Django 1.11

Questions:
Answers:

FYI: in case someone else runs into the same two problems I encountered:

  1. You should still declare any permanently readonly_fields in the body of the class, as the readonly_fields class attribute will be accessed from validation (see django.contrib.admin.validation: validate_base(), line.213 appx)

  2. This won’t work with Inlines as the obj passed to get_readonly_fields() is the parent obj (I have two rather hacky and low-security solutions using css or js)

Questions:
Answers:

You can do this by overriding the formfield_for_foreignkey method of the ModelAdmin:

from django import forms
from django.contrib import admin

from yourproject.yourapp.models import YourModel

class YourModelAdmin(admin.ModelAdmin):

    class Meta:
        model = YourModel

    def formfield_for_foreignkey(self, db_field, request=None, **kwargs):
        # Name of your field here
        if db_field.name == 'add_only':
            if request:
                add_opts = (self._meta.app_label, self._meta.module_name)
                add = u'/admin/%s/%s/add/' % add_opts
                if request.META['PATH_INFO'] == add:
                    field = db_field.formfield(**kwargs)
                else:
                    kwargs['widget'] = forms.HiddenInput()
                    field = db_field.formfield(**kwargs)
            return field
        return admin.ModelAdmin(self, db_field, request, **kwargs)

Questions:
Answers:

Got a similar problem. I solved it with “add_fieldsets” and “restricted_fieldsets” in the ModelAdmin.

from django.contrib import admin  
class MyAdmin(admin.ModelAdmin):
 declared_fieldsets = None
 restricted_fieldsets = (
    (None, {'fields': ('mod_obj1', 'mod_obj2')}),
    ( 'Text', {'fields': ('mod_obj3', 'mod_obj4',)}),
 )

 add_fieldsets = (
            (None, {
             'classes': ('wide',),
             'fields': ('add_obj1', 'add_obj2', )}),
             )

Please see e.g.: http://code.djangoproject.com/svn/django/trunk/django/contrib/auth/admin.py

But this doesn’t protect your model from later changes of “add_objX”.
If you want this too, I think you have to go the way over the Model class “save” function and check for changes there.

See: www.djangoproject.com/documentation/models/save_delete_hooks/

Greez, Nick

Questions:
Answers:

A variation based on the previous excellent suggestion of Bernhard Vallant, which also preserves any possible customization provided by the base class (if any):

class MyModelAdmin(BaseModelAdmin):

    def get_readonly_fields(self, request, obj=None):
        readonly_fields = super(MyModelAdmin, self).get_readonly_fields(request, obj)
        if obj: # editing an existing object
            return readonly_fields + ['field1', ..]
        return readonly_fields