chosa91

# A Best in Class Checklist
A boiled down checklist adapted from this [post](https://www.swiftjectivec.com/a-best-in-class-app/), created by @jordanmorgan10.

> To use this, create a Github Issue in your own repo, and simply copy and paste this text.

## iOS Core Technology
_Things any iOS app can benefit from_

- [ ] iCloud Sync
- [ ] [Core Spotlight integration](https://github.com/DreamingInBinary/Spend-Stack/issues/120)

chosa91

extension FileManager {
    /*
        Prints out the locations of the simulator and the shared group folder.
        This is useful for debugging file issues.

        Example usage: FileManager.default.printFileLocations()
     */
    func printFileLocations() {
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        let simulatorFolder = paths.last!

chosa91

// Avoids the keyboard in a UIKit app by leveraging additionalSafeAreaInsets.
// You can put this in the root view controller so the whole app will avoid the keyboard.
// Only tested on iOS 13.3.
// Made for https://douglashill.co/reading-app/
@objc func updateSafeAreaForKeyboardFromNotification(_ notification: Notification) {
    guard let endFrameInScreenCoords = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect else {
        return
    }

    // Please consider whether the force unwrap here is safe for your own use case.

chosa91

@discardableResult
public func with<T>(_ value: T, _ builder: (T) -> Void) -> T {
    builder(value)
    return value
}

@discardableResult
public func with<T>(_ value: T, _ builder: (T) throws -> Void ) rethrows -> T {
    try builder(value)
    return value

chosa91

struct StateMachine<State, Action> {
  private(set) var state: State
  private let transition: (State, Action) -> State?

  init(startState: State, transition: @escaping (State, Action) -> State?) {
    self.state = startState
    self.transition = transition
  }

  mutating func apply(action: Action) -> Bool {

chosa91

libdispatch efficiency tips

I suspect most developers are using the libdispatch inefficiently due to the way it was presented to us at the time it was introduced and for many years after that, and due to the confusing documentation and API. I realized this after reading the 'concurrency' discussion on the swift-evolution mailing-list, in particular the messages from Pierre Habouzit (who is the libdispatch maintainer at Apple) are quite enlightening (and you can also find many tweets from him on the subject).

• https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170828/date.html
• https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170904/date.html
• https://twitter.com/pedantcoder

My take-aways are:

chosa91

ℹ️ This article is also available on his blog.

---

Fundamentals

Layout and Drawing are two different things:

• Layout defines only the positions and sizes of all views on screen.
• Drawing specifies how each view is rendered (how it looks).

chosa91

import XCTest

@_functionBuilder
struct Test<T> {
    var data: T
    var given: given<T>
    var when: when<T>
    var then: then<T>

    func execute() {

chosa91

// Douglas Hill, November 2019

import UIKit

/// A scroll view that allows scrolling using a hardware keyboard like `NSScrollView`.
/// Supports arrow keys, option + arrow keys, command + arrow keys, space bar, page up, page down, home and end.
/// Limitations:
/// - Paging scroll views (isPagingEnabled = true) are not supported yet.
/// - The scroll view must become its own delegate so setting the delegate is not supported yet.
/// - Does not consider zooming. This has not been tested at all.

chosa91

import Foundation

struct AnyEquatable {
    private let isEqualTo: (Any) -> Bool
    let value: Any
    
    init<A: Equatable>(_ value: A) {
        self.value = value
        isEqualTo = { other in
            guard let o = other as? A else { return false }