In a Django form, how to make a field readonly (or disabled) so that it cannot be edited

djangofieldformsreadonly

In a Django form, how do I make a field read-only (or disabled)?

When the form is being used to create a new entry, all fields should be enabled – but when the record is in update mode some fields need to be read-only.

For example, when creating a new Item model, all fields must be editable, but while updating the record, is there a way to disable the sku field so that it is visible, but cannot be edited?

class Item(models.Model):
    sku = models.CharField(max_length=50)
    description = models.CharField(max_length=200)
    added_by = models.ForeignKey(User)


class ItemForm(ModelForm):
    class Meta:
        model = Item
        exclude = ('added_by')

def new_item_view(request):
    if request.method == 'POST':
        form = ItemForm(request.POST)
        # Validate and save
    else:
            form = ItemForm()
    # Render the view

Can class ItemForm be reused? What changes would be required in the ItemForm or Item model class? Would I need to write another class, "ItemUpdateForm", for updating the item?

def update_item_view(request):
    if request.method == 'POST':
        form = ItemUpdateForm(request.POST)
        # Validate and save
    else:
        form = ItemUpdateForm()

Best Answer

As pointed out in this answer, Django 1.9 added the Field.disabled attribute:

The disabled boolean argument, when set to True, disables a form field using the disabled HTML attribute so that it won’t be editable by users. Even if a user tampers with the field’s value submitted to the server, it will be ignored in favor of the value from the form’s initial data.

With Django 1.8 and earlier, to disable entry on the widget and prevent malicious POST hacks you must scrub the input in addition to setting the readonly attribute on the form field:

class ItemForm(ModelForm):
    def __init__(self, *args, **kwargs):
        super(ItemForm, self).__init__(*args, **kwargs)
        instance = getattr(self, 'instance', None)
        if instance and instance.pk:
            self.fields['sku'].widget.attrs['readonly'] = True

    def clean_sku(self):
        instance = getattr(self, 'instance', None)
        if instance and instance.pk:
            return instance.sku
        else:
            return self.cleaned_data['sku']

Or, replace if instance and instance.pk with another condition indicating you're editing. You could also set the attribute disabled on the input field, instead of readonly.

The clean_sku function will ensure that the readonly value won't be overridden by a POST.

Otherwise, there is no built-in Django form field which will render a value while rejecting bound input data. If this is what you desire, you should instead create a separate ModelForm that excludes the uneditable field(s), and just print them inside your template.

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Firefox 30 ignores autocomplete="off" for passwords, opting to prompt the user instead whether the password should be stored on the client. Note the following commentary from May 5, 2014:

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R – How to pass a User model into a form field (django)

maybe something like this - override the save() method where you can call encrypt method.

for decrypt you can use signal post_init, so every time you instantiate the model from the database the product_id field is decrypted automatically

class MyClass(models.Model):
    user_field = models.ForeignKey(User)
    product_id = EncryptedCharField()
    ...other fields...

    def save(self):
        self.product_id._encrypt(product_id, self.user_field)
        super(MyClass,self).save()

    def decrypt(self):
        if self.product_id != None:
            user = self.user_field
            self.product_id._decrypt(user=user)

def post_init_handler(sender_class, model_instance):
    if isinstance(model_instance, MyClass):
        model_instance.decrypt()

from django.core.signals import post_init
post_init_connect.connect(post_init_handler)


obj = MyClass(user_field=request.user) 
#post_init will be fired but your decrypt method will have
#nothing to decrypt, so it won't garble your input
#you'll either have to remember not to pass value of crypted fields 
#with the constructor, or enforce it with either pre_init method 
#or carefully overriding __init__() method - 
#which is not recommended officially

#decrypt will do real decryption work when you load object form the database

obj.product_id = 'blah'
obj.save() #field will be encrypted

maybe there is a more elegant "pythonic" way of doing this

Best Answer

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