WWDC19

• 244: Visual Design Accessibility
• 413: Testing in Xcode
• 415: Modern Swift API Design
• 429: LLDB: Beyond “po”
• 707: Advances in App Background Execution
• 723: Advances in Foundation

244: Visual Design Accessibility

1. Dynamic Type
2. Reduce Motion
   • 一些人对动态效果感知非常强烈，甚至引起焦虑，需要关闭。
3. Differentiate Without Color
   • 针对色盲用户

413: Testing in Xcode

• Test Plans
• Continuous integration workflows

    $ xcodebuild build-for-testing
    $ xcodebuild test-without-building
    $ xcodebuild -project ... -scheme ... -showTestPlans
    $ xcodebuild test -project ... -scheme ... -testPlan 'Smoke Tests'
    $ man xcodebuild.xctestrun
  	
    $ xcodebuild test
    -project MyProject.xcodeproj
    -scheme MyScheme
    -resultBundlePath /path/to/ResultBundle.xcresult
    $ xcrun xcresulttool get --path ResultBundle.xcresult --format json
    $ xcrun xcresulttool formatDescription get
    $ man xcresulttool
  	
    $ xcrun xccov view --report ResultBundle.xcresult
  

415: Modern Swift API Design

1. Values and references
   • wwdc15/#414-building-better-apps-with-value-types-in-swift

   Choosing — Reference or Value?

   Prefer structs over classes

   • Only choose classes when reference semantics are important

   Classes can make a good choice when

   • You need a reference counting and deinitialization

   • The value is held centrally and shared

   • Where there is a separate notion of “identity” from “equality”

   • Only choose classes when reference semantics are important

2. Protocols and generics

3. Key path member lookup
   • Swift Evolution: SE-0252
   • @dynamicMemberLookup

    class Texture: NSObject {
        var isSparkly: Bool = true
    }
    @dynamicMemberLookup
    struct DynamicStruct {
        private var _texture: Texture = .init()
        subscript<T>(dynamicMember keyPath: ReferenceWritableKeyPath<Texture, T>) -> T {
            get { _texture[keyPath: keyPath] }
            set {
                if !isKnownUniquelyReferenced(&_texture) { _texture = _texture.copy() as! Texture  }
                _texture[keyPath: keyPath] = newValue
            }
        }
    }
    let m = DynamicStruct()
    print(m.isSparkly)
   

4. Property wrappers
   • Swift Evolution: SE-0258
   • @LateInitialized, @DefensiveCopying

    @propertyWrapper
    struct UserDefault<T> {
        let key: String
        let defaultValue: T
        var wrappedValue: T {
            get {
                return UserDefaults.standard.object(forKey: key) as? T ?? defaultValue
            }
            set {
                UserDefaults.standard.set(newValue, forKey: key)
            }
        }
    }
    enum GlobalSettings {
        @UserDefault(key: "FOO_FEATURE_ENABLED", defaultValue: false)
        static var isFooFeatureEnabled: Bool
        /*
         Compiler-synthesized code...

         static var $isFooFeatureEnabled: UserDefault<Bool> = UserDefault<Bool>(key: "FOO_FEATURE_ENABLED", defaultValue: false)
         static var isFooFeatureEnabled: Bool {
             get { $isFooFeatureEnabled.wrappedValue }
             set { $isFooFeatureEnabled.wrappedValue = newValue }
         }
         */
    }
   

429: LLDB: Beyond “po”

1. po
   • po is an abbreviation for expression -O --
   • po Under the Hood: (lldb)po view -> Create compilable code -> Compile -> Execute -> Create code to access description -> Compile -> Execute -> Get string result -> Display result string
   • use: Object description
2. p
   • p is an abbreviation for expression --
   • p Under the Hood: (lldb)p view -> Create compilable code -> Compile -> Execute -> Dynamic type resolution -> Formatter -> Display result string
   • use: Data formatters
3. v
   • v is an abbreviation for frame variable
   • v Under the Hood: (lldb) v variable -> Examine program state -> Read value from memory -> Dynamic type resolution -> Formatter
   • use: Data formatters
4. Customizing Data Formatters
   • type filter
   • type summary
5. Python Formatter, CustomReflectable

707: Advances in App Background Execution

1. Different Use Cases(后台用例)

    //Gives app additional time to run in the background before being suspended
    UIApplication.beginBackgroundTask(expirationHandler:)
   	
    //静默推送, Must set apns-priority = 5 or app will not launch
    //Should set apns-push-type = background
    Muted Threads/Background push
   	
    //Background fetch
    UIApplication.setMinimumBackgroundFetchInterval(_:) 
    UIApplicationDelegate.application(_:performFetchWithCompletionHandler:)
   	
    //Discretionary Background URL Session
    let config = URLSessionConfiguration.background(withIdentifier: "com.app.attachments") 
    let session = URLSession(configuration: config, delegate: ..., delegateQueue: ...)
   	
    //Phone Calls
    VoIP push notifications
   

2. New BackgroundTasks Framework

723: Advances in Foundation

1. Ordered Collection Diffing
2. Data
   • Contiguity
   • DataProtocol
   • MutableDataProtocol
   • Compression
3. Units and Formatters
   • RelativeDateTimeFormatter
   • ListFormatter
4. OperationQueue
   • addBarrierBlock
   • Progress reporting
5. USB and SMB on iOS
6. Swift Update
   • Scanner