Question

models.py:

class Tag(models.Model):
    name = models.CharField(max_length=100)
    description = models.CharField(max_length=500, null=True, blank=True)
    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now_add=True)

class Post(models.Model):
    user = models.ForeignKey(User)
    tag = models.ManyToManyField(Tag)
    title = models.CharField(max_length=100)
    content = models.TextField()
    created = models.DateTimeField(default=datetime.datetime.now)
    modified = models.DateTimeField(default=datetime.datetime.now)

    def __unicode__(self):
        return '%s,%s' % (self.title,self.content)


class PostModelForm(forms.ModelForm):
    class Meta:
        model = Post


class PostModelFormNormalUser(forms.ModelForm):
    class Meta:
        model = Post
        widgets = { 'tag' : TextInput() }
        exclude = ('user', 'created', 'modified')

    def __init__(self, *args, **kwargs):
        super(PostModelFormNormalUser, self).__init__(*args, **kwargs)      
        self.fields['tag'].help_text = None

views.py:

    if request.method == 'POST':
        form = PostModelFormNormalUser(request.POST)
        print form
        print form.errors           
        tagstring = form.data['tag']
        splitedtag = tagstring.split()

        if form.is_valid():
            temp = form.save(commit=False)
            temp.user_id = user.id
            temp.save()

            l = len(splitedtag)         
            for i in range(l):
                obj = Tag(name=splitedtag[i])
                obj.save()
                post.tag_set.add(obj)

            post = Post.objects.get(id=temp.id)
            return HttpResponseRedirect('/viewpost/' + str(post.id))
    else:
        form = PostModelFormNormalUser()
        context = {'form':form}
        return render_to_response('addpost.html', context, context_instance=RequestContext(request))

Here form.is_valid() is always false because it gets the tag as string from form. But it expects list as form.data[‘tag’] input. Can anyone tell me how can i fix it?

How can i write a custom widget to solve this?

Answer 1

I don’t think you need a custom widget (you still want a TextInput), you want a custom Field. To do this, you should subclass django.forms.Field. Unfortunately the documentation is scant on this topic:

If the built-in Field classes don’t meet your needs, you can easily create custom Field classes. To do this, just create a subclass of django.forms.Field. Its only requirements are that it implement a clean() method and that its init() method accept the core arguments mentioned above (required, label, initial, widget, help_text).

I found this blog post that covers both custom widgets and fields in more depth. The author disagrees with the documentation I quoted above – it’s worth reading over.

For your specific situation, you would do something like this (untested):

class MyTagField(forms.Field):
    default_error_messages = {
        'some_error': _(u'This is a message re: the somr_error!'),
    }

    def to_python(self, value):
        # put code here to coerce 'value' (raw data from your TextInput)
        # into the form your code will want (a list of Tag objects, perhaps)

    def validate(self, value):
        if <not valid for some reason>:
            raise ValidationError(self.error_messages['some_error'])

Then in your ModelForm:

class PostModelFormNormalUser(forms.ModelForm):
    tag = MyTagField()

    class Meta:
        model = Post
        exclude = ('user', 'created', 'modified')

    def __init__(self, *args, **kwargs):
        super(PostModelFormNormalUser, self).__init__(*args, **kwargs)      
        self.fields['tag'].help_text = None