[Zope3-Users] ForbiddenAttribute: ('append', []) using append on PersistentList

[Achim Domma]

Hi,

I have implemented a view for a catalog index. The page template 
contains this little form to add strings to a list of categories:

<form action="@@add_category" method="post">
     <input type="text" name="name">
     <input type="submit">		
</form>

The view class looks like this:

class EditView(object):
     def categories(self):
         return self.context.categories

     def add_category(self,name):
         self.context.categories.append(name)

Together they are registered as:

     <browser:page
     	name="categories.html"
     	title="Categories"
     	menu="zmi_views"
     	permission="zope.ManageServices"
     	for="proCoders.interfaces.ICategoryIndex"
     	class=".CategoryIndex.EditView"
     	template="CategoryIndex.pt"
     	/>
     	
     <browser:page
     	for="proCoders.interfaces.ICategoryIndex"
     	name="add_category"
     	class=".CategoryIndex.EditView"
     	attribute="add_category"
     	permission="zope.ManageServices"/>

If I submit the form, add_category is called, but I get the following error:

ForbiddenAttribute: ('append', [])

Any hint what I'm doing wrong?

regards,
Achim