On Sunday, June 23, 2002, at 10:50 AM, Nick Zitzmann wrote:
> OK, I've RTFM'd and don't see much documentation out there on sorting
> NSMutableArrays, so I thought I'd ask...
>
> I'd like to create a new data type that includes an NSString, an
> integer, and access methods for both the NSString and integer. Then I'd
> like to create objects of this type and store them into an
> NSMutableArray. (I've done this many times before.) Finally, I'd like
> to sort the NSMutableArray from time to time so the array is sorted in
> descending order based on the integer value within the object.
>
> I see NSMutableArray has two ways of sorting arrays, but both depend on
> external functions and there is no documentation on what I need to do
> to get this to work. I have no idea where to start... And I'd like to
> avoid bubble sorting if I can.
>
> So how do I go about defining and writing this function? Or are there
> some frameworks out there that do something like this already? Thanks...
In the documentation for NSMutableArray, we have:
- (void)sortUsingSelector:(SEL)comparator
Sorts the receiver's elements in ascending order, as determined by the
comparison method specified by the selector comparator. The comparator
message is sent to each object in the array, and has as its single
argument another object in the array. The comparator method is used to
compare two elements at a time and should return NSOrderedAscending if
the receiver is smaller than the argument, NSOrderedDescending if the
receiver is larger than the argument, and NSOrderedSame if they are
equal.
See Also: - sortUsingFunction:context:, - sortedArrayUsingSelector:
(NSArray)
So, if your class looks like this:
@interface Foo : NSObject {
NSString *name;
int value;
}
- (NSString *)name;
- (int)value;
@end
then you should add a comparison method to Foo, similar to this:
@implementation Foo (SortingByValueDescending)
- (NSComparisonResult) compareByValueDescending:(Foo *)other {
if ([self value] == [other value]) {
return NSOrderedSame;
} else if ([self value] < [other value]) {
return NSOrderedDescending;
} else {
return NSOrderedAscending;
}
}
@end
and then you can use this as follows,
NSMutableArray *foos;
foos = [foos sortUsingSelector:@selector(compareByValueDescending:)];
> Nick Zitzmann
// Christian Brunschen
