https://github.com/lxcid/listdiff

Swift port of IGListKit's IGListDiff
https://github.com/lxcid/listdiff

diff swift swift-port

Last synced: 1 day ago
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Swift port of IGListKit's IGListDiff

• Host: GitHub
• URL: https://github.com/lxcid/listdiff
• Owner: lxcid
• License: mit
• Created: 2016-10-22T14:53:53.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2020-06-27T07:59:22.000Z (over 4 years ago)
• Last Synced: 2024-11-14T17:03:54.901Z (1 day ago)
• Topics: diff, swift, swift-port
• Language: Swift
• Homepage:
• Size: 41 KB
• Stars: 241
• Watchers: 8
• Forks: 23
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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[![CocoaPods Compatible](https://img.shields.io/cocoapods/v/ListDiff.svg)](https://cocoapods.org/pods/ListDiff)

# ListDiff

__ListDiff__ is a Swift port of [IGListKit](https://github.com/Instagram/IGListKit)'s [IGListDiff](https://github.com/Instagram/IGListKit/blob/master/Source/IGListDiff.mm).

It is an implementation of [an algorithm by Paul Heckel](http://dl.acm.org/citation.cfm?id=359467&dl=ACM&coll=DL) that calculates the diff between 2 arrays.

## Motivation

The motivation for this project came from the following [challenge](https://github.com/Instagram/IGListKit/issues/76) which I learnt about it from [Ryan Nystrom](https://twitter.com/_ryannystrom)'s [talk](https://engineers.sg/video/scaling-at-large-lessons-learned-rewriting-instagram-s-feed-ios-conf-sg-2016--1218) at [iOSConf.SG](http://iosconf.sg).

## Getting Started

```bash

swift package generate-xcodeproj

```

## Installation

#### CocoaPods

```ruby

pod 'ListDiff'

```

#### Carthage

```ogdl

github "lxcid/ListDiff" "master"

```

## Usage

```swift

import ListDiff

extension Int : Diffable {

    public var diffIdentifier: AnyHashable {

        return self

    }

}

let o = [0, 1, 2]

let n = [2, 1, 3]

let result = List.diffing(oldArray: o, newArray: n)

// result.hasChanges == true

// result.deletes == IndexSet(integer: 0)

// result.inserts == IndexSet(integer: 2)

// result.moves == [List.MoveIndex(from: 2, to: 0), List.MoveIndex(from: 1, to: 1)]

// result.changeCount == 4

```

## Rationale

During the port, I made several decisions which I would like to rationalize here.

- _Using caseless enum as namespace._ See [Erica Sadun's post here](http://ericasadun.com/2016/07/18/dear-erica-no-case-enums/).

- _No support for index paths._ Decided that this is out of the scope.

- _Stack vs Heap._ AFAIK, Swift does not advocates thinking about stack vs heap allocation model, leaving the optimization decisions to compiler instead. Nevertheless, some of the guideline do favour `struct` more, so only `List.Entry` is a (final) class as we need reference to its instances.

## Alternatives

- [Diff](https://github.com/AndrewSB/Diff) by [Andrew Breckenridge](https://github.com/AndrewSB)