best way to implement privacy on each field in model django

Question

I am trying to provide privacy settings at the model's field level for users. So a user can decide which data he wants to display and which data he wants to hide.

Example:

class Foo(models.Model):
    user = models.OneToOneField("auth.User")
    telephone_number = models.CharField(blank=True, null=True, max_length=10)
    image = models.ImageField(upload_to=get_photo_storage_path, null=True, blank=True)

I want to provide an option to the user to select the fields which he wants to display and which he doesn't. Consider a user doesn't want to display telephone_number, so he should have the option for that.

Which is the best way to approach this?

Answer 1

You can create a CommaSeparatedIntegerField field inside the model, and use it to store a list of field_names (Integers that denote a field_name) that the user wants to hide.

You can create a mapping between the field_names and integers as a constant inside your models.py. And check whichever field_names are those the the user had checked.

Example mapping:

FIELD_NAME_CHOICES = (
    (1, Foo._meta.get_field('telephone_number')),
    (2, Foo._meta.get_field('name')),
    .
    .
)

Check the following link for reference https://docs.djangoproject.com/en/1.8/ref/models/fields/#commaseparatedintegerfield

Answer 2

The very obvious plain stupid solution would be to add a boolean 'show_xxx' for each field, ie:

class Foo(models.Model):
    user = models.OneToOneField("auth.User")
    telephone_number = models.CharField(blank=True, null=True, max_length=10)
    show_telephone_number = models.BooleanField(default=True)
    image = models.ImageField(upload_to=get_photo_storage_path, null=True, blank=True)
    show_image = models.BooleanField(default=True)

Then in your templates check for the show_xxx field's value:

{% if foo.telephone_number and foo.show_telephone_number %}
  <p>Telephone number: {{ foo.telephone_number }}</p>
{% endif %}

etc...

Of course you can also use a single integer field and the old bitmask trick:

class Foo(models.Model):
    user = models.OneToOneField("auth.User")
    telephone_number = models.CharField(blank=True, null=True, max_length=10)
    image = models.ImageField(upload_to=get_photo_storage_path, null=True, blank=True)

    foo = models.TextField(blank=True)

    perms = models.IntegerField(default=0)
    SHOW_TEL = 1
    SHOW_IMG = 2
    SHOW_FOO = 4

    def _show(self, flag):
        return (self.perms & flag) == flag

    def show_telephone_number(self):
        return self._show(self.SHOW_TEL)

    def show_image(self):
        return self._show(self.SHOW_IMG)

    def show_foo(self):
        return self._show(self.SHOW_FOO)

but I'm not sure this really is an "optimisation"... And you'll have to manually take care of the checkboxes etc in your edit forms.

Answer 3

You could also use a MultiSelectField... The code below is from a Django Snippets, so please no credits to me as I'm only sharing the work of someone else!

class MultiSelectField(models.CharField):
""" Choice values can not contain commas. """

def __init__(self, *args, **kwargs):
    self.max_choices = kwargs.pop('max_choices', None)
    super(MultiSelectField, self).__init__(*args, **kwargs)
    self.max_length = get_max_length(self.choices, self.max_length)
    self.validators[0] = MaxValueMultiFieldValidator(self.max_length)
    if self.max_choices is not None:
        self.validators.append(MaxChoicesValidator(self.max_choices))

@property
def flatchoices(self):
    return None

def get_choices_default(self):
    return self.get_choices(include_blank=False)

def get_choices_selected(self, arr_choices):
    choices_selected = []
    for choice_selected in arr_choices:
        choices_selected.append(string_type(choice_selected[0]))
    return choices_selected

def value_to_string(self, obj):
    value = self._get_val_from_obj(obj)
    return self.get_prep_value(value)

def validate(self, value, model_instance):
    arr_choices = self.get_choices_selected(self.get_choices_default())
    for opt_select in value:
        if (opt_select not in arr_choices):
            if django.VERSION[0] == 1 and django.VERSION[1] >= 6:
                raise ValidationError(self.error_messages['invalid_choice'] % {"value": value})
            else:
                raise ValidationError(self.error_messages['invalid_choice'] % value)

def get_default(self):
    default = super(MultiSelectField, self).get_default()
    if isinstance(default, (int, long)):
        default = string_type(default)
    return default

def formfield(self, **kwargs):
    defaults = {'required': not self.blank,
                'label': capfirst(self.verbose_name),
                'help_text': self.help_text,
                'choices': self.choices,
                'max_length': self.max_length,
                'max_choices': self.max_choices}
    if self.has_default():
        defaults['initial'] = self.get_default()
    defaults.update(kwargs)
    return MultiSelectFormField(**defaults)

def get_prep_value(self, value):
    return '' if value is None else ",".join(value)

def to_python(self, value):
    if value:
        return value if isinstance(value, list) else value.split(',')

def contribute_to_class(self, cls, name):
    super(MultiSelectField, self).contribute_to_class(cls, name)
    if self.choices:
        def get_list(obj):
            fieldname = name
            choicedict = dict(self.choices)
            display = []
            if getattr(obj, fieldname):
                for value in getattr(obj, fieldname):
                    item_display = choicedict.get(value, None)
                    if item_display is None:
                        try:
                            item_display = choicedict.get(int(value), value)
                        except (ValueError, TypeError):
                            item_display = value
                    display.append(string_type(item_display))
            return display

        def get_display(obj):
            return ", ".join(get_list(obj))

        setattr(cls, 'get_%s_list' % self.name, get_list)
        setattr(cls, 'get_%s_display' % self.name, get_display)

MultiSelectField = add_metaclass(models.SubfieldBase)(MultiSelectField)