Ole Begemann ole

Extract a value from the SwiftUI environment by the name of its associated EnvironmentKey (e.g. "ForegroundColorKey").

Tested only in Xcode 12.0 beta 4 in the iOS simulator. May break in other environments because it uses reflection. If SwiftUI's private type hierarchy changes, it will probably stop working.

	// A view that can flip between its "front" and "back" side.
	//
	// Animation implementation based on:
	// Chris Eidhof, Keyframe animations <https://gist.github.com/chriseidhof/ea0e435197f550b195bb749f4777bbf7>

	import SwiftUI

	// MARK: - Chris's keyframe animation design

	struct Keyframe<Data: Animatable> {

	// 1. Run on iPad simulator in landscape (= two-column navigation view).
	// 2. Drill down to level 3
	// 3. Observe console output.
	//
	// Result with .navigationViewStyle(.stack) (as expected):
	// Level 1: drilledDown=false
	// Level 1: drilledDown=true
	// Level 2: drilledDown=false
	// Level 2: drilledDown=true
	// Level 3: drilledDown=false

	import SwiftUI

	struct ContentView: View {
	@State var horizontal: Bool = true
	@Namespace var namespace

	var body: some View {
	VStack(spacing: 40) {
	if horizontal {
	HStack { items }

	import Foundation

	struct ContainerEncoded: Encodable {
	var date: Date = .now

	func encode(to encoder: Encoder) throws {
	var container = encoder.singleValueContainer()
	try container.encode(date)
	}
	}

	let precomposed = "é"
	let decomposed = "e\u{301}"
	// `==` for strings means canonically equivalent:
	assert(precomposed == decomposed)

	let letters = "ffi"
	let ligature = "ﬃ"
	// The ligature and its decomposition are not canonically equivalent:
	assert(letters != ligature)

	let evens = Array(1...10)
	.lazy
	.filter { $0.isMultiple(of: 2) }
	evens.indices // → [1, 3, 5, 7, 9]
	evens[0] // → 1 (🤯!)

	import Foundation

	let date = Date.now
	date.formatted(.iso8601) // "20210618T191800Z"
	date.formatted(.iso8601.year().month().day().dateSeparator(.dash)) // "2021-06-18"
	date.formatted(.iso8601.dateSeparator(.dash).timeSeparator(.colon)) // "2021-06-18T19:18:00Z"

	/*:
	Joe Groff:

	> In a lot of the ways people use dictionaries/maps/hashtables, there's a type dependency between
	> the keys and values, but most mainstream typed languages provide homogeneously-typed maps.
	> Are there any that try to preserve more interesting type relationships between key and value?
	> https://twitter.com/jckarter/status/1278739951568314368

	> As one example, it's common for specific keys to be associated with specific types, like in
	> {"name": "Tanzy", "age": 13}, "name" should always map to a string, and "age" to a number.

	import SwiftUI

	struct ContentView: View {
	var body: some View {
	VStack {
	// Why is the rectangle drawn out of bounds of the stack view?
	Rectangle().fill(Color.green)
	.frame(width: 100, height: 40)
	.alignmentGuide(HorizontalAlignment.center) { _ in 0 }
	}