At 06:15 PM 10/12/00 +1100, Itai Tavor wrote:
Hi, ...... 2. I want to store a list of products, and give each one an arbitrary number of photos. I can use a Product ZClass, subclassed from ObjectManager and store Image objects inside it. But what will happen to these objects if I use this ZClass in a Rack? And how would I handle storing the objects in SQL tables - I will need to somehow turn each Image object into a table entry, and the same Generic Attribute Provider will have to work with 2 SQL tables. Is there a nice way of doing this? Or should I store the photos in a separate ZClass and use it in another Rack in the Products Specialist?
I would not suggest trying to go the ObjectManager route. ZPatterns does not have a good way at present to map child objects into other databases. Instead, a more custom approach would be appropriate, where you have say an "images" attribute that is loaded/saved through SQL. This has the downside, however, of being either resource intensive or computationally intensive.
However, it'd probably be best of all to have a Photos specialist, with a getPhotosForProduct() method, addPhotoToProduct(), and so on.
Why would I want another Specialist for photos? Photos are just another attribute of a Product. They just happen to be stored separately, a distinction which I think should happen at the Rack level. I created my Products Specialist with 3 racks: 'defaultRack' for Product properties, 'photoRack' for photos, and 'priceRack' for product price options (every product can have multiple price options, so I don't store a price in the product properties). Then I can have methods in each Rack to deal with the specific object stored in it, and methods in the Specialist to handle the overall view. I can also have a SkinScript in the defaultRack to return a virtual Product object which includes a list of photo objects. Is there anything wrong with this?
Actually, I can't put an Image object on a DataSkin, right? So however I store it, it's going to have to be a my own custom Image object subclassed from DataSkin...
Not necessarily, it depends on your overall structure. If you want to use standard Zope Image objects you may indeed want to subclass from DataSkin.
I do want to use the standard Zope Image object - it's got a lot of useful functions that I don't want to lose and I don't want to do the work of writing my own Image class and duplicating all those functions. But I don't know how to get the Image product to store in a DataSkin - or if it's possible at all. If I create a ZClass subclassing Image and DataSkin, would the image data automatically get stored in the DataSkin? Or do I have to override all methods dealing with storage in the object? Also, the Image __init__ methd requires a file - Image objects can't be created empty, but the DataSkin always creates new objects with no data, so I guess some overriding will be required to allow the object to function empty... Itai -- Itai Tavor "Je sautille, donc je suis." C3Works itai@c3works.com - Kermit the Frog "If you haven't got your health, you haven't got anything"