lattner

Swift Concurrency Manifesto

Author: Chris Lattner

Chinese Translation by Jason Yu

Contents

• Introduction
• Overall Vision

andymatuschak

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

steipete

// Taken from the commercial iOS PDF framework http://pspdfkit.com.
// Copyright (c) 2014 Peter Steinberger, PSPDFKit GmbH. All rights reserved.
// Licensed under MIT (http://opensource.org/licenses/MIT)
//
// You should only use this in debug builds. It doesn't use private API, but I wouldn't ship it.

// PLEASE DUPE rdar://27192338 (https://openradar.appspot.com/27192338) if you would like to see this in UIKit.

#import <objc/runtime.h>
#import <objc/message.h>

timonus

- (UIImage *)dynamicImage
{
    UITraitCollection *const baseTraitCollection = /* an existing trait collection */;
    UITraitCollection *const lightTraitCollection = [UITraitCollection traitCollectionWithTraitsFromCollections:@[baseTraitCollection, [UITraitCollection traitCollectionWithUserInterfaceStyle:UIUserInterfaceStyleLight]]];
    UITraitCollection *const purelyDarkTraitCollection = [UITraitCollection traitCollectionWithUserInterfaceStyle:UIUserInterfaceStyleDark];
    UITraitCollection *const darkTraitCollection = [UITraitCollection traitCollectionWithTraitsFromCollections:@[baseTraitCollection, purelyDarkTraitCollection]];
    
    __block UIImage *lightImage;
    [lightTraitCollection performAsCurrentTraitCollection:^{
        lightImage = /* draw image */;

AdamLantz

//Swift 4 modifications for this gist: https://gist.github.com/krooked/9c4c81557fc85bc61e51c0b4f3301e6e
import Foundation
import UIKit

extension UIImage {
    func cropImageByAlpha() -> UIImage {
        let cgImage = self.cgImage
        let context = createARGBBitmapContextFromImage(inImage: cgImage!)
        let height = cgImage!.height
        let width = cgImage!.width

alessaba

// Swift Playgrounds Beta 1.0
import AVFoundation
import AVKit
import Accelerate
import Accounts
import AudioToolbox
import AudioUnit
import CFNetwork
import CoreAudio
import CoreAudioKit

airspeedswift

postfix operator ..< { }
prefix operator ..< { }

struct RangeStart<I: ForwardIndexType> { let start: I }
struct RangeEnd<I: ForwardIndexType> { let end: I }

postfix func ..<<I: ForwardIndexType>(lhs: I) -> RangeStart<I>
{ return RangeStart(start: lhs) }

prefix func ..<<I: ForwardIndexType>(rhs: I) -> RangeEnd<I>

fastred

Results of searching for NS_SWIFT_UNAVAILABLE macro in iOS 9 and OS X 10.11 headers reveal some new Swift-specific APIs.

Highlights

GameplayKit.framework/Headers/GKEntity.h
70: - (nullable GKComponent *)componentForClass:(Class)componentClass
NS_SWIFT_UNAVAILABLE("Exposed in Swift as componentForClass<ComponentType: GKComponent>(componentClass: ComponentType.Type) -> ComponentType?");

GameplayKit.framework/Headers/GKStateMachine.h

zats

#!/usr/bin/env xcrun swift

// $ chmod +x script.swift
// $ ./script.swift
// or $ ./script.swift -xcode=/Applications/Xcode-beta.app

import Foundation

@noreturn private func failWithError(message: String) {
    print("🚫 \(message)")

dennisvennink

extension Sequence {
  var headAndTail: (head: Element, tail: SubSequence)? {
    var head: Element?

    let tail = drop {
      if head == nil {
        head = $0

        return true
      } else {