GAE forms

To validate a form one could validate with javascript clientside. I too want form validation, preview, blobstore, i18n and edit items preferably with no thirdparty libraries so trying to learn how with a Form class with BlobStore blobs I got this in the upload handler ie a BlobstoreUploadHandler that uploads a blobstore blob using a form class ...

blob_info = self.get_uploads()[0] 

data = AForm(data=self.request.POST) 

entity = data.save(commit=False) 

entity.put() 

im = Image(reference=entity) 

im.primary_image = blob_info.key() 

im.put() entity.put()

... Dispatching to upload handling is a view class that renders self.render_template("upload.html", { 'form': form, 'form_url': blobstore.create_upload_url('/fileupload'),
Then I enabled the form page to also able to edit an item

if self.request.get('id'): 

a = A.get_by_id(long(self.request.get('id'))) 

form = AForm(instance = a) 

else: form = AForm() 

After that I too have issues with validation and preview where BlobStore seems doable to fit in a form.
My form class is

class AForm(djangoforms.ModelForm): 

text = forms.CharField(widget=forms.Textarea(attrs={'rows':'11','cols':'70','class':'foo'}),label=_("content").capitalize()) 

class Meta: 

model = A 

fields = ['category','currency','price','title','phonenumber','postaladress','name','text','email'] #change the order
I now hope we can recommend or comment how to enable validation and preview the "official" way. Since django.contrib.formtools.preview appears built in GAE it could be good to first try what the SDK provides to minimize thirdparty library dependency. I didn't look at formish yet and will do so onwards.