Hi James,
The ComparisonSupport becomes transparent and used universally throughout
the app. Here's an excerpt of one place where a sort occurs:
NSMutableArray displayedObjects = <the objects to display in a paginated
list on the screen>
NSMutableArray sortOrderings = <a list of EOSortOrdering objects taking a
key and an NSSelector>
EOSortOrdering.sortArrayUsingKeyOrderArray(displayedObjects,
sortOrderings);
This is often called by clicking a little toggle icon to modify the
"sortOrderings" array with a particular "key" and either
"compareAscending" or "compareDescending".
It works like a charm. The null values are placed at the very end of an
ascending sort and placed at the beginning of a descending sort. It works
so long as we haven't done any commits to the database. Sounds odd, I
know, because I don't fully understand what is happening. It probably
isn't the commit to the database itself but some other nuance. All I know
with certainty is that I can move around the whole app and happily re-sort
columns anywhere but as soon as I do a commit I'm no longer able to
reliably sort columns on any page. Also, once it gets in this bad state,
any new wosessions I start exhibit the same problem immediately.
-- Aaron
James Cicenia <[EMAIL PROTECTED]> wrote on 31-01-2008 02:01:03 PM:
> What do you mean it no longer works after commits?
>
> How are you using your comparator?
>
> -James Cicenia
>
> On Jan 31, 2008, at 12:34 PM, [EMAIL PROTECTED] wrote:
>
>
> What happens when you want to sort ten values in ascending order but
> one of them is null? Does that void value get put at the beginning,
> the middle, or the end?
>
> Apple decided that null values (or keyPaths that return a null
> value) should be placed at the beginning of an array sorted in
> ascending order. Perhaps they felt that "null is less than zero".
>
> For us, it seems that null values should be placed at the end of an
> ascending sort. More often than not, null values make more sense to
> be placed at the end of the list when working in our Domain.
>
> Has anyone crossed this bridge before?
>
> We've tried our hand at a solution which is listed at the bottom of
> this message. It works so long as no commits have been made to the
> database! After a commit, from any page in the app, sorting no
> longer works as expected and often results in a K2Sort error. It's
baffling.
>
> Our class extends the default sorting logic of EOSortOrdering.
> ComparisonSupport (the class that does sorting globally for WO). We
> really only want to override "handleNulls()" but because it is both
> private and static, we need to redo a few other methods as well.
> Functionally, our class is identical but choose to place null values
> at the end of the list for an ascending sort.
>
> Here is the line we add to the Appliction's constructor to get the
> ball rolling globally:
> ==========================
>
> EOSortOrdering.ComparisonSupport.setSupportForClass(new
> CXNullsAtEndComparisonSupport(), Object.class);
>
>
> Here is the source code to the custom ComparisonSupport:
> ==========================
>
> public class CXNullsAtEndComparisonSupport extends EOSortOrdering.
> ComparisonSupport {
>
> public static final Logger _logger = Logger.
> getLogger(CXNullsAtEndComparisonSupport.class);
>
> public CXNullsAtEndComparisonSupport() {}
>
> protected static final int kNeitherNull = -42;
>
> protected static int handleNulls(Object left, Object right)
> {
> if(left == null || left == NSKeyValueCoding.NullValue)
> return right != null && right !=
> NSKeyValueCoding.NullValue ? NSComparator.OrderedDescending :
> NSComparator.OrderedSame;
> return right != null && right != NSKeyValueCoding.
> NullValue ? kNeitherNull : NSComparator.OrderedAscending;
> }
>
> private static final NSTimestampFormatter
> defaultStringTimestampFormatter = new NSTimestampFormatter("%Y-%m-%d
> %H:%M:%S %Z");
>
> protected static NSTimestamp coerceToTimestampClass(Object
value)
> {
> if(value instanceof NSTimestamp)
> return (NSTimestamp)value;
> if(value instanceof Date)
> return new NSTimestamp(((Date)value).getTime());
> if(value instanceof Number)
> return new
NSTimestamp(((Number)value).longValue());
> try {
> return (NSTimestamp)
> defaultStringTimestampFormatter.parseObject((String)value);
> } catch (Exception e) {
> //fixme: do something more.
> _logger.info("coerceToTimestampClass failed.
> Message = " + e.getMessage());
> return null;
> }
> }
>
> protected int _genericCompareTo(Object left, Object right)
> {
> int nullCheck = handleNulls(left, right);
> if(nullCheck != kNeitherNull) {
> return nullCheck;
> }
> Class LHSClass = left.getClass();
> if(LHSClass == _NSUtilities._StringClass)
> return
left.toString().compareTo(right.toString());
> if((left instanceof Number) || LHSClass ==
> _NSUtilities._BooleanClass)
> return _NSUtilities.
> compareNumbersOrBooleans(left, right);
> if(left instanceof Date)
> {
> if(LHSClass != NSTimestamp._CLASS)
> left = coerceToTimestampClass(left);
> right = coerceToTimestampClass(right);
> }
> if(left instanceof Comparable)
> return ((Comparable)left).compareTo(right);
> else
> return
left.toString().compareTo(right.toString());
> }
>
> protected int _genericCaseInsensitiveCompareTo(Object left,
> Object right)
> {
> int nullCheck = handleNulls(left, right);
> if(nullCheck != kNeitherNull)
> return nullCheck;
> Class LHSClass = left.getClass();
> if(LHSClass == _NSUtilities._StringClass)
> return left.toString().
> compareToIgnoreCase(right.toString());
> if((left instanceof Number) || LHSClass ==
> _NSUtilities._BooleanClass)
> return _NSUtilities.
> compareNumbersOrBooleans(left, right);
> if(left instanceof Date)
> {
> if(LHSClass != NSTimestamp._CLASS)
> left = coerceToTimestampClass(left);
> right = coerceToTimestampClass(right);
> return ((Comparable)left).compareTo(right);
> } else
> {
> return left.toString().
> compareToIgnoreCase(right.toString());
> }
> }
>
> } _______________________________________________
> Do not post admin requests to the list. They will be ignored.
> Webobjects-dev mailing list ([email protected])
> Help/Unsubscribe/Update your Subscription:
>
http://lists.apple.com/mailman/options/webobjects-dev/james%40jimijon.com
>
> This email sent to [EMAIL PROTECTED] _______________________________________________
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list ([email protected])
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to [EMAIL PROTECTED]
