TL;DR;

Bad UX	Good UX1

¹: Slowed down intentionally to demonstrate the awesomeness

Problems it solves

• Calculating mutations is too hard and you're just calling reloadData on your collection or table view?
• Users, confused where did that row disappear?
• Rows, jumping out of nowhere?
• Lost scroll position?

Doppelganger is here to help!

Usage

NSArray *oldDataSource = self.dataSource;
self.dataSource = [self _updatedDataSource];
NSArray *diffs = [WMLArrayDiffUtility diffForCurrentArray:self.dataSource
                                            previousArray:oldDataSource];
[self.tableView wml_applyBatchChanges:diffs
                            inSection:0
                     withRowAnimation:UITableViewRowAnimationRight];

Implementation details

• Currently, doppelganger supports only array of unique elements, e.g. if you have duplicated elements in your array, result is unpredictable.
• If you are using custom classes, make sure that it implements correctly isEqual: and hash methods: http://nshipster.com/equality/
• Sections are not handled intentionally. From our experience sections are harder to match using strict equality + hashing. However, if this is your case, feel free to use Doppelganger for sections, too.

TODOs

• Improve on O(n²) when calculating moved elements.
• Abstract API from NSArray.
• Your issue / pull request.

Installation

Author

Sash Zats, [email protected]

License

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