inverse()

Declaration

func inverse() -> Self

Return Value

A copy of the receiver with all removals changed to insertions (and vice versa).

Discussion

Applying a difference to an ordered collection and then applying the inverse difference results in the original ordered collection:

NSArray *original = @[@"1", @"2"];
NSArray *modified = [original arrayByAddingObject:@"3"];

NSOrderedCollectionDifference *diff = [modified differenceFromArray:original];

NSArray *updated = [original arrayByApplyingDifference:diff];
// updated == [@"1", @"2", @"3"] == modified

NSOrderedCollectionDifference *inverse = [diff inverseDifference];

updated = [updated arrayByApplyingDifference:inverse];
// updated == [@"1", @"2"] == original