Re: What happened to automatic binary primary keys?

I believe they may still exist if you set the primary key type to 
NSData with a width of 24. You can also create them yourself by 
implementing EODatabaseContext's delegate method 
databaseContextNewPrimaryKey. The easiest size to generate is 24 bytes, 
just use EOTemporaryGlobalID's assignGloballyUniqueBytes. For smaller 
sizes you'd want to do a hash of some sort.

In WireHose 2.0 we use this method along with EOModelGroup's 
subEntityForEntity delegate method to optionally encode entity 
information in the primary key, which can be useful for avoiding extra 
fetches when resolving to-one faults against abstract entities.

In WireHose 1.0, we took a different approach, which was to create a 
JDBC plug in wrapper which only implemented the newPrimaryKeys method 
and delegated all other methods to the wrapped plugin. Implementing the 
databaseContextNewPrimaryKey method is easier. :-)

Here's a simple implementation:

public NSDictionary databaseContextNewPrimaryKey(EODatabaseContext 
databaseContext, Object object, EOEntity entity) {
	if (entity.primaryKeyAttributeNames().count() != 1) { // don't handle 
compound primary keys
	   return null;
	}
	EOAttribute primaryKeyAttribute = 
(EOAttribute)entity.primaryKeyAttributes().objectAtIndex(0);
	if (primaryKeyAttribute.adaptorValueType() != 
EOAttribute.AdaptorBytesType) { // only handle NSData primary keys
		return null;
	}
	int pkWidth = primaryKeyAttribute.width();
	if (pkWidth == EOTemporaryGlobalID.UniqueBinaryKeyLength) {
		String primaryKeyAttributeName = primaryKeyAttribute.name();
		byte[] hashBytes = new 
byte[EOTemporaryGlobalID.UniqueBinaryKeyLength];
		EOTemporaryGlobalID.assignGloballyUniqueBytes(hashBytes);
		return new NSDictionary(new NSData(hashBytes), 
primaryKeyAttributeName);
	} else {
		return null;
	}	
}

On Tuesday, March 25, 2003, at 12:46  AM, Ashley Aitken wrote:

> I browsed Apple's documentation, Omnigroup's mailing lists, googled 
> here
> and googled there, but I can't find anything about those globally 
> unique
> binary keys that EOF used to be able to generate automatically.  I 
> think
> they were 12 bytes then jumped to 20 (or was that) 24 bytes.  They were
> made up, IIRC, of an IP address, an entity name, etc etc.
>
> Do these still exist in WO 5.2.x?  Can someone please point me to some
> documentation?   Or do they just automatically if you declare the
> primary key to be NSData with external type something like Byte width 
> of
> 20 etc?

-- 
Gary Teter, Big Dog
Bulldog Beach Interactive http://www.bulldogbeach.com
WireHose: Powerful WebObjects content management
http://www.wirehose.com