Zope form : adding a button to automatically fill some fields - forms

Question

under Plone4/Zope3, I have a form to add a new object.
I'd like to add a button after the first field, to do the following :
- the user enters the value for the first field
- he presses this new button
- and the server will try to guess the remaining field based on the first field and an external database.
- the user will then have to check if all fields are OK and then submit the form.
I am not a zope expert, and spent some time trying to figure out how to do this.
Is creating a subform a good idea ?
If not, I could add a new button to the form : I tried something like
#button.buttonAndHandler(_(u'Essai'))
def essai(self, action):
print "button essai"
but then I have the following issues :
- how to render the button after the first field and not at the bottom ?
- how to update the remaining fields without submitting the form ?
- how to keep the "add" and "cancel" button that disappeared when I added this essai button.
any hints ?
Thx

Answer 1

I suggest to use javascript to solve this. With jquery you can include an extra button directly behind your first field (http://api.jquery.com/after). In the button action ask a browser view for the search results in json (http://docs.python.org/library/json.html) an fill up the other form fields, like:
jq('my-button').click(function(event) {
event.preventDefault();
var first_field= jq('#first-field-id').val();
jq.getJSON('/##my-browser-view?value=' + value, function(result) {
jq('#other-field-id').val(result.val_for_other_field);
...
});
});