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Hacking in Swift

Adrian M. DevAndArtist

Hacking in Swift
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View UnconstrainedEnvironmentObject.swift
import SwiftUI
extension EnvironmentValues {
struct UnconstrainedObjectKey<Object>:
Object: AnyObject
static var defaultValue: Object? {
View ReferenceFileDocument_Example.swift
import SwiftUI
import UniformTypeIdentifiers
extension UTType {
static var exampleText: UTType {
UTType(importedAs: "com.example.plain-text")
DevAndArtist / CustomStateObject.swift
Last active December 15, 2021 17:36
Custom `StateObject` which should be backwards compatible with iOS 13.
View CustomStateObject.swift
import SwiftUI
import Combine
/// The idea is to use State to create a storage object which will be
/// cached and restored by the framework. Then during the update phase we
/// re-inject the object into a nested ObservableObject and subscribe to the
/// ObjectType’s objectWillChange to forward to the _MessageForwarder’s
/// objectWillChange which is already subscribed by the framework as it’s an
/// inner dynamic property of our custom PW which is also a dynamic property.
View interchangeable_matched_geometry_effect.swift
import SwiftUI
struct HeroAnimationTest: View {
let indices = 0 ..< 3
var showsOtherView = false
var namespaceID: Namespace.ID
View swiftui_picker_attempt.swift
import Combine
import SwiftUI
// To re-align the cells to the center we use a workaround through debouncing
// the nearest cell ID which is computed every time the scroll view moves.
// HOWEVER there is a bug that still needs to be solved:
// If you drag the scroll view and hold, the debounce event will still happen
// and reposition the cell.
View weak_as_type.swift
import PlaygroundSupport
import Dispatch
let page = PlaygroundPage.current
page.needsIndefiniteExecution = true
struct Weak<T> {
struct _ObjectBox {
weak var object: AnyObject?
View small_but_shiny.swift
public protocol MapKey {
associatedtype Value
static var defaultValue: Value { get }
public struct Map<Base> {
typealias _Key = ObjectIdentifier
var _values: [_Key: Any]
View swiftui_alignment_keys.swift
import SwiftUI
// T.Type -> AlignmentID.Type -> Any.Type -> UInt
extension HorizontalAlignment {
enum TestH: AlignmentID {
static func defaultValue(in context: ViewDimensions) -> CGFloat {
View broken_swiftui_layout.swift
// BUG: FB7635852
import SwiftUI
struct ContentView: View {
let count: Int
var body: some View {
.init(alignment: .top, spacing: 0) {
View swiftui_update_inconsistency.swift
// * In Xcode 11.3.1 `V_Struct_Representable_ObservedObject` won't update
// which is clearly a bug. This bug is fixed in Xcode 11.4 beta 1.
// * `V_Struct` and `V_Struct_Representable` both never update because
// they shouldn't as the framework internal raw-diffing likely won't
// identify any change. (EXPECTED BEHAVIOR)
// * `V_Class` and `V_Class_ObservedObject` both produce a runtime crash,
// which might be a bug as well. `View` conforming types shouldn't be