Resort

Resort is a small library that builds comparators from key paths, combines separate comparators into compound ones, and can build reverse comparators.

Key Path Comparators

Sorting from a keyPath would be a very straightforward thing to do, if it weren't for the edge cases. This library deals with nil and NSNull values and offers special handling of those, like always-less and always-greater comparison. It uses always-less as a pragmatic default. But if that's not what you need you can specify that nil should always be treated as greater. Or you might want to fail fast and throw an exception.

Order is defined for the classes in Foundation that support it already via compare: methods: NSString, NSDate, NSNumber, NSIndexPath, as well as their subclasses, e.g. NSMutableString and NSDecimalNumber.

In other cases, the comparator just performs the ordering on the -description of the object.

Compound Comparators

Comparators build from key paths are very similar to NSSortDescriptors, but the have the advantage to be easy to combine. This is what the other half of the library is about, compound comparators. Think of it as a simple, composable way to define a sort order with primary, secondary, and so on sort keys.

Usage

To run the example project; clone the repo, and run pod install from the Example directory first.

Creation and use of a keyPath comparator looks like this:

NSComparator comparator = [RESResort comparatorForKeyPath:@"name"];
NSArray *sorted = [@[ z, a ] sortedArrayUsingComparator:comparator];

Two comparators (keyPath based or otherwise) can be combined into a compound comparator and used like this:

NSComparator nameComparator = [RESResort comparatorForKeyPath:@"name"];
NSComparator countComparator = [RESResort comparatorForKeyPath:@"count"];
NSComparator compoundComparator = [RESResort compoundComparatorWithComparatorArray:@[ nameComparator, countComparator ]];
NSArray *sorted = [_array sortedArrayUsingComparator:compoundComparator];

Requirements

Only Foundation framework. Tested on iOS 7 and OS X 10.9.

Author

Florian Ebeling, florian.ebeling@gmail.com

License

Resort is available under the MIT license. See the LICENSE file for more info.