Consider wrapping the get/change/put in a transaction: http://code.google.com/appengine/docs/python/datastore/transactions.html
On Jan 25, 9:28 pm, David Kamenetz <[email protected]> wrote: > I finally got this working. > > My python module looked something like this: > > from google.appengine.ext.db import Key > from google.appengine.api.datastore import Get, Put > > def edit_item(request, db_id): > > objKey = Key(str(db_id)) > > if request.method == 'POST': > objEntity = Get(objKey) > for k, v in request.POST.iteritems(): > objEntity[k]=v > Put(objEntity) > return HttpResponseRedirect('/') > > query = TestModel.get(objKey) > return render_to_response('edit.html', ({'modify_data': query,})) > > My HTML looked something like this: > > <form method="POST" action="." enctype="multipart/form-data"> > Title: <input type="text" name="title" > value="{{modify_data.field1}}"/> > Text: <input type="text" name="txt" value="{{modify_data.field2}}"/> > > <input type="submit"/> > </form> > > Many thanks to Bill! > > On Jan 24, 10:32 pm, David Kamenetz <[email protected]> wrote: > > > Thanks Bill, that was helpful. I had been browsing datastore.py in the > > SDK, but I wasn't quite sure how to use it. Your solution gave me a > > lot of ideas. > > > Regards, > > David > > > On Jan 24, 7:11 pm, Bill <[email protected]> wrote: > > > > Hi David, > > > > On Jan 24, 8:39 am, David Kamenetz <[email protected]> wrote: > > > > > However, if the user only enters/changes, say, the txt field on the > > > > form I only POST the txt field to the server. I don't send all the > > > > fields. My POST only has data for txt. If I use the code above on an > > > > existing entity, it will erase the title property (formitem.title). > > > > > Is there an elegant way to write only the txt element to the txt > > > > property? > > > > As far as I know, you can't write only one property when replacing an > > > existing entity, but maybe there's something that can be done at the > > > lowest levels just before going to the protocol buffer. (See > > > datastore.py and datastore_pb.py in the SDK where entity dicts are > > > being passed.) > > > > I use POSTs to create new entities and PUTs to modify existing ones or > > > store a new entity in a known url. With the PUTs, if there's an > > > existing entity, you need to read it in and then selectively modify > > > key/values depending on what's been passed from your form. > > > > So creating new entities through POST is simple. Just set whatever > > > property you want to set on model initialization, and all others are > > > not stored. > > > > You can automate the whole process by creating a Model you'll inherit > > > from (I call mine SerializableModel), and create a method that > > > iterates through all model properties, calls request.get() on them, > > > and if the get isn't None (i.e., there's a value passed in from your > > > form), you add that key/value to your entity dict. You later pass the > > > entity dict as an initializer into your Model constructor. > > > > For example: > > > > def get_entity_dict(model_class, get_func): > > > entity_dict = {} > > > for prop_name, prop_class in model_class.properties().iteritems(): > > > value = get_func(prop_name) > > > if value: > > > entity_dict[prop_name] = model_class.deserialize > > > (prop_class, value) > > > return entity_dict > > > > So in the above, get_func is set to: > > > > get_func = lambda x : some_handler.request.get(x, default_value=None) > > > > We only set key/value pairs in entity_dict for properties that are set > > > in form. > > > > The model_class.deserialize() is a routine that takes strings from the > > > form and converts them into appropriate datastore objects. > > > > So in your handler you'd have something like this in simplified form: > > > > def post(self): > > > get_func = lambda x : some_handler.request.get(x, > > > default_value=None) > > > props = get_entity_dict(MyModel, get_func) > > > obj = MyModel(**props) > > > obj.put() > > > > For the PUT case, you read the entity first, set the entity_dict to > > > the current entity values, and then do the above. > > > > I might open source the model system I've created that does all this > > > stuff. > > > > -Bill --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
