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());
}
}
} _______________________________________________
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