Split field to array when accessed

Question

I have Django model that looks like this:

class Categories(models.Model):
    """
    Model for storing the categories
    """
    name = models.CharField(max_length=8)
    keywords = models.TextField()
    spamwords = models.TextField()
    translations = models.TextField()

    def __unicode__(self):
        return self.name

    class Meta:
        verbose_name = _('Category')
        verbose_name_plural = _('Categories')

The fields keywords, spamwords and translations contain huge chunks of comma-separated text. Could someone tell how I could write a function inside the model which for a particular fieldname, returns the value a list so that I could access it something like this:

cat = Categories.objects.get(id=1)
print cat.keywords.to_array()

...it returns the field data, split into an array. (The splitting bit is very simple and i know how to do that - string.split(',')

Thanks

Answer 1

You can easily add an instance method to your Categories class like this:

class Categories(models.Model):
   ... rest of your definition ...

   def get_spamwords_as_list(self):
       return self.spamwords.split(',')

You could use it like this:

cat = Categories.objects.get(id=1)
print cat.get_spamwords_as_list()

But I'm curious about your underlying data model -- why aren't you using a ManyToManyField to model your categories?

UPDATE: Adding an alternative generic version:

def get_word_list(self, name):
    if name in ['keywords', 'spamwords', 'translations']:
        return getattr(self, name).split(',')

# or even
def __getattr__(self, name):
    if name[-5:] == '_list' and name[:-5] in ['keywords', 'spamwords', 'translations']:
        return getattr(self, name[:-5]).split(',')
    else
        raise AttributeError

cat = Categories.get(pk=1)
cat.get_word_list('keywords')  # ['word 1', 'word 2', ...]
cat.keywords_list              # ['word 1', 'word 2', ...] with 2nd approach
cat.keywords                   # 'word 1, word 2' -- remains CSV

Answer 2

I did it this way:

class Categories(models.Model):
    """
    Model for storing the categories
    """
    name = models.CharField(max_length=8)
    keywords = models.TextField()
    spamwords = models.TextField()
    translations = models.TextField()

    def __unicode__(self):
        return self.name

    def __getattribute__(self, name):
        if name not in ['keywords', 'spamwords', 'translations']:
            return object.__getattribute__(self, name)
        else:
            return object.__getattribute__(self, name).split(',')

    class Meta:
        verbose_name = _('Category')
        verbose_name_plural = _('Categories')