While fixing bug 595163[1] I found out that there is a provision for this type of errors in LaunchpadBrowserRequest. I pasted the documentation for it below for your convenience.
I am wondering, though, why we could not give BrowserFormNG a full dict interface (it already implements __contains__ and __iter__) and let it replace the normal 'form' attribute completely. Saves at least three characters in line length ... ;-) Cheers, Henning [1] https://bugs.launchpad.net/rosetta/+bug/595163 == Handling form data using IBrowserFormNG == Submitted form data is available in the form_ng request attribute. This is an object providing the IBrowserFormNG interface which offers two methods to obtain form data. (Form data is also available through the regular Zope3 form attribute using the dictionary interface.) >>> from canonical.launchpad.webapp.interfaces import IBrowserFormNG >>> verifyObject(IBrowserFormNG, request.form_ng) True You can check the presence of an uploaded field using the regular python 'in' operator. >>> from canonical.launchpad.webapp.servers import ( ... LaunchpadBrowserRequest) >>> from urllib import urlencode >>> environment = {'QUERY_STRING': urlencode({ ... 'a_field': 'a_value', ... 'items_field': [1, 2, 3]}, doseq=True)} >>> request = LaunchpadBrowserRequest('', environment) >>> request.processInputs() >>> 'a_field' in request.form_ng True >>> 'another_field' in request.form_ng False The advantage of the IBrowserFormNG API is that it offers methods that checks the number of values you are expecting. The getOne() method should be used when you expect only one value for the field. >>> request.form_ng.getOne('a_field') u'a_value' UnexpectedFormData is raised if more than one value was submitted for the field: >>> request.form_ng.getOne('items_field') Traceback (most recent call last): ... UnexpectedFormData:... None is returned if the field wasn't submitted: >>> request.form_ng.getOne('another_field') is None True You can provide a default value that is returned if the field wasn't submitted: >>> request.form_ng.getOne('another_field', u'default') u'default' The getAll() method should be used when you are expecting a list of values. >>> request.form_ng.getAll('items_field') [u'1', u'2', u'3'] If only one value was submitted, it will still be returned as part of a list: >>> request.form_ng.getAll('a_field') [u'a_value'] An empty list is returned when no value was submitted for the field: >>> request.form_ng.getAll('another_field') [] That method also accepts a default value that is to be returned when no value was submitted with the field. >>> request.form_ng.getAll('another_field', [u'default']) [u'default'] All the submitted field names can be iterated over: >>> for name in sorted(request.form_ng): ... print name a_field items_field _______________________________________________ Mailing list: https://launchpad.net/~launchpad-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~launchpad-dev More help : https://help.launchpad.net/ListHelp
