Sorting with sortedArrayUsingDescriptors and Key Paths

Question

I have an unordered array with instances of the following class:

@interface Place : NSObject {

}

@property (nonatomic, copy) NSString *country;
@property (         


        

Answer 1

You may want to use this:

NSSortDescriptor *country = [[[NSSortDescriptor alloc] initWithKey:@"country" ascending:YES]autorelease];
NSSortDescriptor *city = [[[NSSortDescriptor alloc] initWithKey:@"city" ascending:YES]autorelease];
NSArray *sorted = [bag sortedArrayUsingDescriptors:[NSArray arrayWithObjects: country, city, nil]];

The array that's passed to sortedArrayUsingDescriptors: defines the sorting key priorities. The sort descriptors provide the keypaths to compare (and the wanted order: ascending/descending).

A sort descriptor of "country.city" will ask each place for its country and then as the returned country (which is an NSString) for its city. And we all know that NSString is not value coding-compliant for the key city ;)

You'd need a sort descriptor of "country.city" if your Place instances had a property country, which themselves had a property city.