Re: EOF Design Questions

Hi Ashley,


Ashley Aitken wrote:
> The standard use of EOF is something like this:
>
> Fetch a number of EOs into an EC (as needed).
> Make changes to some or all of the EOs, i.e. EOi(StateAi) ---> 
> EOi(StateBi)
> Add some new EOs or delete some of the fetched EOs
>
> I am wondering how to the following efficiently, after the above:
>
> Clone all the EOs in the EC that have been change, i.e. EOi(StateBi) 
> ---> EOj(StateBi)
> Revert only the original EOs to their fetched state, i.e. EOi(StateBi) 
> ---> EOi(StateAi)
> Note: Any deleted EOs would not be cloned but still reverted, i.e. 
> no-longer deleted
> Make some more changes to the original fetched EOs, i.e. EOi(StateAi) 
> ---> EOi(StateCi)
> Save all the originally fetched EOs and new EOs i.e. ec.saveChanges()
> Note: The new EOs include (really) new EOs and cloned EOs.
>
> I've looked at the APIs for EC and EOGenericRecord and nothing pops 
> out, specifically with respect to:
>
> 1.  How best to clone an EO in an EC?
> Create and insert a new EO, transfer state, ...


You can define an abstract superclass (i.e. ClonableGenericRecord) for 
all your cloneable entities extending EOGenericRecord Cloneable with a 
method that does something like this:

	public EOEnterpriseObject clone() {
		Enumeration keys;
		EOEnterpriseObject object;
		Object value;
		String key;

		object = 
EOClassDescription.classDescriptionForEntityName(entityName()).
			createInstanceWithEditingContext(editingContext(), null);

		keys = allPropertyKeys().objectEnumerator();
		while(keys.hasMoreElements()) {
			key = (String)keys.nextElement();
			object.takeValueForKey(valueForKey(key));
		} // while

		return(object);
	} // clone

But this clone the targeted entity only, i.e. all relationships will be 
same for both the original and the cloned entity:

	EOA.toEOB -> clone -> EOA'.toEOB

If you want to clone entities in relationships as well like this:

	EOA.toEOB -> clone -> EOA'.toEOB'

Then you'll have to modify the clone() loop to build one for each 
attributeKeys(), toOneRelationshipKeys() and toManyRelationshipKeys() 
instead of using allPropertyKeys().


> 2.  How best to revert some EOs (but not all) in the EC?
> Using the original snapshot ... but could that change (is that a 
> problem)?


You can use the editing context revert() method.  Setting up the 
original snapshot shouldn't be a problem though.


--
Francis Labrie
Saint-Bruno-de-Montarville, Quebec, Canada