init the DS only once in the model, so u always have a reference to it
so in GetAllProductsCommand:
ds.fill(model.products)
in LoadProductCommad:
product = Product(myDataGrid.selectedItem);
...
now the Ui edits the product object
so in SaveProductCommand:
ds.commit();
Dimitrios Gianninas
RIA Developer
Optimal Payments Inc.
From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL
PROTECTED]
Sent: Friday, February 23, 2007 1:43 PM
To: flexcoders@yahoogroups.com
Subject: [flexcoders] FDS and Cairngorm / Individual Item Updates
Hey All,
I'm having an issue finding a best-practice approach for CRUD operations with
FDS. Create/Read/Delete are easy, I'm having a problem with updates.
I can easily encapsulate CRD's in my Commands, but there doesn't seem to be an
option to explicitly commit only a single record with FDS.
In a non-cairngorm application, this is pretty easy, I can create a record,
then call ds.createItem(), update it and then ds.commit(). The DataService
object is local to the interface that is managing the record. No problem, one
record committed (correct?).
However, with Cairngorm:
1. Get a list of records
a. dispatch ProductEvent.GET_ALL
b. GetAllProductsCommand.execute()
c. ds = new DataService(productHome);
d. ds.fill(model.products);
2. Edit a product
a. myList.dataProvider = model.products
b. dispatch ProductEvent.EDIT, event.product = myList.selectedItem
c. interface changes to the product form
d. make modifications via a form
e. dispatch ProductEvent.SAVE, event.product = myform.product
f. SaveProductCommand.execute()
g. ds = new DataService(productHome);
h. .. how do we commit just this one record?
Even if I still had a reference to the original DataService from the fill
operation, I may not want to commit all records that changed, only the one that
I'm interested in. This would be equivalent to keeping my DataService in my
ServiceLocator.
The only other option I can think of is that SaveProductCommand works like
this, which messes up conflict checks:
1. product = (event as ProductEvent).product;
2. ds = new DataService(productHome);
3. ds.getItem({product_id: product.product_id});
4. locally synchronize the item retrieved from ds.getItem() with the
product we received in the product event
5. ds.commit()
When we do this though, we very likely have the most recent copy of the object
from the database, so we're not sure that something hadn't changed before
getting it.
Am I making this too complex? Is there another way to simply commit one
particular record? I can think of all sorts of workarounds, but all of them
violate the Cairngorm protocols. I can definitely see the other developers on
the team bypassing our Command logic making Cairngorm a little useless :-)
Jay Proulx
Application Developer
Internet Delivery Services - eVision Team
[EMAIL PROTECTED] mailto:[EMAIL PROTECTED]
(613) 783-6711
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