| extension Collection { | |
| func parallelMap<T>( | |
| parallelism requestedParallelism: Int? = nil, | |
| _ transform: @escaping (Element) async throws -> T | |
| ) async throws -> [T] { | |
| let defaultParallelism = 2 | |
| let parallelism = requestedParallelism ?? defaultParallelism | |
| let n = self.count | |
| if n == 0 { |
On Mac, SwiftUI's .onHover closure is not always called on mouse exit, particularly with high cursor velocity. A grid of targets or with finer target shapes will often have multiple targets falsely active after the mouse has moved on.
It is easy to run back to AppKit's safety. Below is a SwiftUI-like modifier for reliable mouse-tracking. You can easily adapt it for other mouse tracking needs.
import SwiftUI
| extension Collection { | |
| func parallelMap<T>( | |
| parallelism requestedParallelism: Int? = nil, | |
| _ transform: @escaping (Element) async throws -> T | |
| ) async throws -> [T] { | |
| let defaultParallelism = 2 | |
| let parallelism = requestedParallelism ?? defaultParallelism | |
| let n = self.count | |
| if n == 0 { |
| // See commentary below this gist. | |
| import Foundation | |
| import QuartzCore | |
| // Implementation from https://talk.objc.io/episodes/S01E90-concurrent-map | |
| public final class ThreadSafe<A> { | |
| var _value: A | |
| let queue = DispatchQueue(label: "ThreadSafe") | |
| init(_ value: A) { self._value = value } | |
| import UIKit | |
| #if canImport(SwiftUI) && DEBUG | |
| import SwiftUI | |
| struct UIViewControllerPreview<ViewController: UIViewController>: UIViewControllerRepresentable { | |
| let viewController: ViewController | |
| init(_ builder: @escaping () -> ViewController) { | |
| viewController = builder() | |
| } |
This is the example code from my video about using async/await with Cloud Functions. I've placed it here in a gist so it's easier to compare the "before" and "after" states for each case.
The code in this project is licensed under the Apache License 2.0.
Copyright 2018 Google LLC
The libdispatch is one of the most misused API due to the way it was presented to us when it was introduced and for many years after that, and due to the confusing documentation and API. This page is a compilation of important things to know if you're going to use this library. Many references are available at the end of this document pointing to comments from Apple's very own libdispatch maintainer (Pierre Habouzit).
My take-aways are:
You should create very few, long-lived, well-defined queues. These queues should be seen as execution contexts in your program (gui, background work, ...) that benefit from executing in parallel. An important thing to note is that if these queues are all active at once, you will get as many threads running. In most apps, you probably do not need to create more than 3 or 4 queues.
Go serial first, and as you find performance bottle necks, measure why, and if concurrency helps, apply with care, always validating under system pressure. Reuse
This proposal introduces the concept of pure functions to Swift. A pure function is guarantied to allow only value semantics, even when dealing with classes.
Author: Chris Lattner
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.