NEW: Start my new Ultimate Portfolio App course with a free Hacking with Swift+ trial! >>

How to compress and decompress data

Swift version: 5.2

Paul Hudson    @twostraws   

Apple gives us dedicated API for compressing binary data, although annoyingly it exists on NSData without being bridged neatly to Swift’s native Data type. Fortunately, that conversion is trivial, so this functionality isn’t hard to use.

Here’s how to use it:

do {
    let compressedData = try (yourData as NSData).compressed(using: .lzfse)
    // use your compressed data
} catch {
    print(error.localizedDescription)
}

Although it’s common for folks to call compression and decompression zipping and unzipping, zip is one particular file format and the code above uses the LZFSE compression algorithm instead. This an Apple-design compression algorithm that is recommended unless you specifically need one of the others. The alternatives are:

  • .lz4 compresses less effectively, but is significantly faster.
  • .zlib is the recommended general purpose algorithm to use if you want cross compatibility with non-Apple devices.
  • .lzma compresses the most effectively, but should only be used if memory usage and speed are not important. Apple specifically states that this might use a large amount of memory, and so it should be avoided if you’re trying to compress large amounts of data. This is about 10x slower than the alternatives.

If you want to decompress some data, you should use the counterpart method, decompressed(using:), which works in the same way.

Hacking with Swift is sponsored by Fernando Olivares

SPONSORED Would you describe yourself as knowledgeable, but struggling when you have to come up with your own code? Fernando Olivares has a new book containing iOS rules you can immediately apply to your coding habits to see dramatic improvements, while also teaching applied programming fundamentals seen in refactored code from published apps.

Try the book!

Sponsor Hacking with Swift and reach the world's largest Swift community!

Available from iOS 13.0

Similar solutions…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 3.0/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.