Instances of this class are used to perform
multi-level sorts of arrays containging
collections or other objects whose properties can
be obtained using key names.
Returns an autoreleased sort descriptor
initialized to perform comparisons in the
specified order using the comparator to compare
the property aKey of each object.
Returns an autoreleased sort descriptor
initialized to perform comparisons in the
specified order using aSelector to
compare the property aKey of each
object.
Returns the result of comparing object1
to object2 using the property whose key is
defined in the receiver and using the selector of
the receiver. If the receiver performs a descending
order sort, the result of this comparison is the
opposite of that prroduced by applying the
selector.
This method works like this: first, it sorts the
entire contents of the array using the first sort
descriptor. Then, after each sort-run, it looks
whether there are sort descriptors left to process,
and if yes, looks at the partially sorted array, finds
all portions in it which are equal (evaluate to
NSOrderedSame) and applies the following
descriptor onto them. It repeats this either
until all descriptors have been applied or there are
no more equal portions (equality ranges) left in the
array.