Re: Snapshot problems
Re: Snapshot problems
- Subject: Re: Snapshot problems
- From: Chuck Hill <email@hidden>
- Date: Fri, 20 Apr 2007 14:41:20 -0700
On Apr 20, 2007, at 2:28 PM, Steven Mark McCraw wrote:
Another explanation occurred to me. Do you have any custom
attributes in any of the objects? Are any of them mutable (e.g.
NSMutableDictionary, NSMutableArray, a custom class that you wrote)?
Yes, many of my classes have custom attributes. CatalogItem has an
NSMutableDictionary and an NSMutableArray as custom attributes.
DING DING DING! We have a winner!
I believe some of my EOs also have attributes that are references
to custom classes that I have written. Could this be problematic?
Mutable attributes are death to EOF. That is your problem. Or at
least one of them. If you really, really work at it you can probably
get it to work, but it is really not worth the effort IMO. Make them
immutable. Add cover methods to modify these values: make a mutable
clone of the attribute, modify it, make an immutable clone and
replace the attribute value. See page 43 of PWO if you have it. If
you don't have it, can pretty much assure that you want it!
Chuck
Are you doing anything else, anywhere, that might be a departure
from plain jane EOF? You may be doing something that appears
innocent and unrelated which is actually hammering EOF. I am just
trying to prod your memory.
It's hard to know. What is an example of something you would
consider not plain jane EOF? In InventoryItem, I'm overridding the
'set' methods for a couple of attributes that are likely to change
frequently underneath EOF so that it can automatically handle
Optimistic locking exceptions. An example of something like that
is below. Yesterday after some of our email, I got worried that
this may be doing something terrible with regards to EOF, and
commented it all out so that everything was using the default
implementation (and of course this was also the case when I
commented out the entire body of each custom class), but it had no
impact whatsoever on the test case that started all of this, so I
felt more secure that it was ok to do this kind of thing.
public void setShelfQuantity( Number newValue ) {
Integer existingShelf = (Integer) shelfQuantity();
if ( shelfQuantity() != null && availableQuantity() != null &&
rawPrimaryKey() != null ) {
int difference = newValue.intValue() - shelfQuantity
().intValue();
if ( difference >= 0 ) {
increaseShelfQuantityBy( difference );
increaseAvailableQuantityBy( difference );
} else {
reduceAvailableQuantityBy( difference * -1 );
reduceShelfQuantityBy( difference * -1 );
}
} else {
super.setShelfQuantity( newValue );
setAvailableQuantity( newValue );
}
if ( ( existingShelf == null || existingShelf.intValue() == 0 )
&& newValue != null
&& newValue.intValue() > 0 ) {
Enumeration catalogEnum = catalogItems().objectEnumerator();
CatalogItem catalog = null;
while ( catalogEnum.hasMoreElements() ) {
catalog = (CatalogItem) catalogEnum.nextElement();
if ( catalog.futureRelease().intValue() == 1 ) {
catalog.setFutureRelease( new Integer( 0 ) );
}
}
}
}
public void increaseShelfQuantityBy( int numberSold ) {
super.setShelfQuantity( new Integer( shelfQuantity().intValue()
+ numberSold ) );
// try to save changes but check for conflicts
try {
successfulChangeSave();
} catch ( EOGeneralAdaptorException e ) {
// conflict!! try again on the refaulted object
super.setShelfQuantity( new Integer( shelfQuantity().intValue
() + numberSold ) );
try {
successfulChangeSave();
} catch ( EOGeneralAdaptorException f ) {
NSLog.out.appendln( "Multiple conflicts increasing shelf
qty!: " + "shelf: "
+ shelfQuantity() + ", avail: " +
availableQuantity() + "\n"
+ ErrorStackTrace.toString( f ) );
}
}
}
public void refresh() {
editingContext().invalidateObjectsWithGlobalIDs(new NSArray
(editingContext().globalIDForObject(this)));
}
public void successfulChangeSave() throws
EOGeneralAdaptorException {
try {
editingContext().saveChanges();
} catch ( EOGeneralAdaptorException f ) {
refresh();
throw f;
}
if ( editingContext().parentObjectStore() instanceof
EOEditingContext ) {
try {
( (EOEditingContext) editingContext().parentObjectStore
() ).saveChanges();
} catch (EOGeneralAdaptorException f) {
refresh();
throw f;
}
}
}
Chuck
--
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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