On 21 juil. 2009, at 15:19, Francesco Romano wrote:
On 21/lug/09, at 12:43, Christian Trotobas wrote:
On 21 juil. 2009, at 12:19, Francesco Romano wrote:
Thanks to both.
I read that chapter in the Apple documentation.
If I understand correctly the globalID has its scope in the
editingcontext.
I don't know why but I create a new editing context for each
page... so this is bad. Should I keep a single editing context?
(until a customer add the first product in the cart I don't have a
session.., so I don't have access to session
().defaultEditingContext()).
Take a look at EOSharedEditingContext. Seems to me this is what you
are looking for.
http://devworld.apple.com/documentation/InternetWeb/Reference/WO542Reference/com/webobjects/eocontrol/EOSharedEditingContext.html
Search the mailing list for EOSharedEditingContext, too.
Ok.. I read that.
For every read-only fetch I changed
ERXEC.newEditingContext()
with
EOSharedEditingContext.defaultSharedEditingContext();
Except this problem, I can do this: (?)
Number pk = product.primaryKey(); //it's a string.. I'll cast to
number
EOEditingContext ec = ERXEC.newEditingContext()
EOEntity entity = EOModelGroup.defaultGroup().entityNamed
("Product");
EOGlobalID gid = entity.globalIDForRow(new NSDictionary(pk,"id"));
Product p = (product) ec.faultForGlobalID(gid);
Looks good. But Andrew's advice was more an example on how things
work, rather than an advise on what exactly your code should look
like.
Use a shareEditingContext for Products, then a simple
defaultEditingEditing from your Session to store the cart.
Christian
I don't understand " then a simple defaultEditingEditing from your
Session to store the cart."
I thought to use a simple NSMutableArray in the session.
Well... that could work, but you ought to go the EOF way. And it is
something like having an EO to store your customer, then have another
EO to store the cart, then other EO to store the fact that a Product
is in the cart.
Something like :
Customer <-->> Cart ->> Lines -> Product
All but Product "belong" to an editingContext in the Session, aka the
defaultEditingContext to make it simple.
Lines could store the quantity, the price, etc, etc.
Christian
Francesco
Thanks
Francesco
Hello Francesco;
You can construct an EOGlobalID from the primary key an fault
it. I would generally not advocate using the primary key in this
manner as it may be volatile owing to migration of schema or
database product migration. That concern aside, assuming you
have a primary key and it has an attribute name of "id";
Number pk = ???
EOEditingContext ec = ???
EOEntity entity = EOModelGroup.defaultGroup().entityNamed
("FooBar");
EOGlobalID gid = entity.globalIDForRow(new NSDictionary(pk,"id"));
FooBar = (FooBar) ec.faultForGlobalID(gid);
Hope this helps.
cheers.
On 21/lug/09, at 11:24, Christian Trotobas wrote:
Hi Francesco
On 21 juil. 2009, at 09:56, Francesco Romano wrote:
Hi..
This is a simple (and maybe stupid) question.
No question is stupid on this list. Feel free to ask.
I'm doing an application (an e-commerce application.. maybe wo
is not the best choice, but I know java better than ruby..), and
I've some pages accessed with directaction.
WebObjects is a pretty good choice for ecommerce; take a look at
the Apple Store to be sure :)
Maybe I'm wrong, but I can pass values to a page only with the
url, so.. only strings.
In a page I select an EntityObject and I've to pass to the other
page.
If I can't pass the whole object, I would like to pass the
primary key, so fetching should be faster..
But.. I can get the key, but I can't fetch an Object with it's PK.
Now i pass a name (a description string..).. but it's not
unique, so even with low probability, there can be collisions..
You should use a product ID which would be unique, like a part
number for example. It will be usefull too for accounting
purpose, and not only for the app internals. As a unique key, the
PK could be used, but depending on the nature of your business,
you might want to avoid exposing PK on the web: they should be
considered both confidential and subject to changes for technical
reasons (though it is very unlikely to occur).
In WebObjects, the EOF framework provides a unique identifier for
EO: it is the EOGlobalID. Basically, it is a compound from the
EOEntity name and the PK from the table (out of the box, it is
how it works; for specific reason out of the scope of your
question, it happens that it is not the PK; again, it is very
unlikeky to occur for standard/simple uses, so don't bother about
this, it was just for information purpose). Therefore, in your
app, if you are looking for a unique identifier for your EO
objects, you have to use the EOGlobalID and not the PK.
Understanding how EOF handles the uniquing of objects is one the
keys for your successfull development with WebObjects.
Take a close look at:
http://developer.apple.com/documentation/Webobjects/Enterprise_Objects/Fetching/Fetching.html#//apple_ref/doc/uid/TP30001011-CH206-BADHCCEE
Hope that helps.
Christian Trotobas
What can I do?
Thanks
Francesco Romano
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