lattner

Async/Await for Swift

• Proposal: SE-XXXX
• Authors: Chris Lattner, Joe Groff

Introduction

Modern Cocoa development involves a lot of asynchronous programming using closures and completion handlers, but these APIs are hard to use. This gets particularly problematic when many asynchronous operations are used, error handling is required, or control flow between asynchronous calls gets complicated. This proposal describes a language extension to make this a lot more natural and less error prone.

This paper introduces a first class Coroutine model to Swift. Functions can opt into to being async, allowing the programmer to compose complex logic involving asynchronous operations, leaving the compiler in charge of producing the necessary closures and state machines to implement that logic.

mbuchetics

struct User: Codable {
    var name: String
    var email: String
    var id: String
    var metadata: [String: MetadataType]

    enum CodingKeys: String, CodingKey {
        case name, email, id, metadata
    }
}

sbooth

import Foundation

class Test {
	init() {
		print("init")
	}
	deinit {
		print("deinit")
	}
}

algal

// known-good: Xcode 8, Swift 3

import Foundation

var standardError = FileHandle.standardError

extension FileHandle : TextOutputStream {
  public func write(_ string: String) {
    guard let data = string.data(using: .utf8) else { return }

jspahrsummers

//
// DON'T do this, or else you risk a deadlock (e.g., by accidentally performing it in a different order somewhere)
//

dispatch_async(firstQueue, ^{
  dispatch_sync(secondQueue, ^{
    // code requiring both queues
  });
});

dabrahams

Properties

Conclusions After Much Discussion

• Things that produce a logical transformation of the whole value are methods. That includes transformed views such as the result of reverse() on a bidirectional collection.

• Things that mutate state (even state outside the receiver) are methods.

zachbadgett

import Foundation

import IOKit
import IOKit.usb
import IOKit.usb.IOUSBLib

print("Scanning USB Bus.....\n\n\n")

//

baarde

#import <Foundation/Foundation.h>

@protocol OS_Foo <NSObject> @end
typedef NSObject<OS_Foo> * Foo;

@protocol OS_Bar <NSObject> @end
typedef NSObject<OS_Bar> *__attribute__((objc_independent_class)) Bar;

@interface Test : NSObject
@end

broomburgo

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface Optional : NSObject

+ (Optional*)with:(id _Nullable)value;
+ (Optional*)with:(id _Nullable)value as:(Class _Nonnull)valueClass;

chriseidhof

import Cocoa

struct Person {
    var name: String = "John"
    var age: Int = 50
    var dutch: Bool = false
    var address: Address? = Address(street: "Market St.")
}

struct Address {