SwiftLeeds

7th Oct 2020 | Leeds 🏴󠁧󠁢󠁥󠁮󠁧󠁿

Conference Website

Server-side Swift State of the Union: Life after async/await

Tim Condon

• A number of developments in Swift over the last few years to make server side easier
  • Codable
  • Xcode support for SPM
  • Key paths
  • Concurrency
• Upcoming features:
  • Swift Crypto
  • Additional Linux Distros
• Tim Condon believes Swift on the Server IS Ready for Production
• Is being used by:
  • Nodes (Arriva trains)
  • Allegro (like Amazon in Poland)
  • John Lewis
  • BBC (for testing infrastructure)
  • Amazon (part of Prime Video)
  • Spotify (open source contributions to Vapor)
  • Apple (although not clear on the specifics [maybe iCloud?])
• Swift as a language feels in the sweet spot between Go and Rust
• Non-Xcode setup for Vapor is still hard
  • Want to improve it
  • As well on Linux
• async/await is exciting as it provides compiler checks for concurrent code
  • Better than using closures
  • Will add the “missing piece” for server application development
• Task local values will help tracing across micro services
  • Tasks are automatically attached to; no need to pass a context object
  • Unique to Swift over other server-side languages

Using Core Data in a SwiftUI application

Donny Wals

• Core Data is an old ORM and has 16+ years or optimisation
• Although it is not very friendly to Swift, it does work well with SwiftUI
• Use SwiftUI features such as
  • @FetchRequest
  • @SectionFetchRequest
• However using these poses the question - does this leak Core Data into your SwiftUI views?
  • Perhaps not
  • It is really convent even if it does
• Use @State for searching and predate updating
• Using a child context
  • Doesn’t trigger notifications to UI
  • Can be discarded when changes are not wanted
  • Saves into the view context
    • Then save the view context to persist to store
• Use a view model to be responsible for managing the contexts and saving
  • Use an EditAndCreateViewModel for both behaviours to make it easier
• Managed objects can be over served as they support KVO
  • This makes them work well with SwiftUI

Example code repo

🍏 + 🔥 = ❤️ (Firebase for Apple Developers)

Peter Friese

• Bindable items were introduced in WWDC 2021
• When editing don’t want to make changes everywhere
  • Use inner @ObservableObject
  • Like a view model
• Use @ApplicationAppDelegateAdapter to reuse an existing App Delegate

Understanding Data Races and Actors

Antoine van der Lee

Useful links for crashes:

• EXC_BAD_ACCESS

• signal.h(0p) - Linux manual page

• Race conditions can cause weird behaviour
• Data conditions can cause crashes
• Multiple threads access the same value at the same time
• Can use a serial lock queue to stop races
• Actors synchronise mutable state across threads
• All lines in an actor are implicitly isolated
• Mark non-mutable data nonisolated
• Can use the Xcode thread sanitiser
  • Helps to find data races
  • Can do it just on the test suite as it can slow execution down

Understanding and Using the App Store Connect

Josh Holtz

• The old API was not meant for external access
• Developers figured it out through proxies and reverse engineering
• The new API looks like it is is based on the JSON API spec
• Uses JWTs
  • You can create them in a tool like Paw
• The API still has some missing features
  • Cannot upload an .ipa
  • No access token for enterprise accounts
• Spaceship (part of Fastlane) support all new endpoints

There’s no IF OR ELSE. It’s all about YOU

Danijela Vrzan

• Changed career from Civil Engineering to Software Engineering
• Moved from Croatia to Canada
• Is a contribuer to http://raywenderlich.com
  • Writing articles helps to learn subjects
• Don’t be afraid to follow you dream
• Don’t be scared to fail

The life of an Indie Developer

Jordi Bruin

• There are three kinds of indie developer:
  • Tool Builder
  • Beta chaser
  • Nice filler
• Look at the new API from Apple for inspiration
  • Build small apps around them
• Iterate and get user feedback
• Don’t over polish before releasing
• Being featured on the App Store is good
• Better to be features on site like iMore as this drives more traffic
• Find communities your potential users are active in
  • Facebook
  • Reditt
• Ask them for help
  • Give out promo codes
• A passion project can fill a niche
  • Something to work on over time
  • Dedicated core users will pay for your app