I've added a propertysheet called "properties" to my ZClass and i notice there is Persistent Sheetprovider under the default rack already. The Sheetprovider has properties Sheet_Names and Sheet_Namespaces. I guess Sheet_Names should refer to the sheetname i created for my ZClass??? but how do Sheet_Namespaces come into play.
From the IRC_Chatlog: "Call "getItem(key)" to retrieve an item from the Specialist, and "newItem(key)" to create a new item in the specialist."
Does this imply that I can simply call "newItem(key)" from a dtml-method inside the specialist to create a new instance of my object? I think I understand ZPattern architecture somewhat but get lost on the implementation side, particularly at that place where attributes are retrieved from storage or more clearly how a specialist(datamanager) links up/communicates with a sheetprovider (data-plugin) and how the sheetprovider in turn communicates with the rack and how the rack retrieves from storage (dataskin). A very simple outline like this would help me a lot, eg: Specialist to Sheetprovider (handled in IDE - add a SheetProvider under Plugins) Sheetprovider to rack (handled in IDE - select Storage Class under rack) Rack to Dataskin (????) Dataskin to physical storage (????) Roché PS: I would be more than willing to document my enlightenment in a howto
-----Original Message----- From: alexande@cat-box.net [mailto:alexande@cat-box.net]On Behalf Of Steve Alexander Sent: 07 August 2000 06:19 To: RC Compaan; zope-dev@zope.org Subject: Re: [Zope] ZPatterns Question
I've moved your question to zope-dev, as that's where ZPatterns questions probably belong.
Roche wrote:
I created a ZClass called "Product" with Dataskin as baseclass.
I also added a specialist called ProductManager containing a default rack. Under storage for the rack I selected the newly created Product ZClass.
My product ZClass needs to query both a RDBMS and the ZODB for attributevalues. At this point I get lost. I guess i should add an attributeprovider plug-in???
The easiest way is to use a couple of SheetProviders. Use a PersistentSheetProvider for your ZODB values. You'll have to write your own one for SQL values.
You will need to create the appropriate propertysheets in your ZClass class definition in your product.
What should go into the fromexpr and attrsexprs properties of the attributeprovider? Should one add an attributeprovider for each attribute of the product?
See the IRC chat log:
http://www.zope.org/Documentation/Chats/zpatt_chat_log An attribute provider can provide multiple attributes. You can have multiple attribute providers if you like. -- Steve Alexander Software Engineer Cat-Box limited http://www.cat-box.net