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anandabits / list-overlay-clipping.swift
Last active Nov 17, 2020
SwiftUI List overlay clipping
View list-overlay-clipping.swift
// NOTE: behavior is exhibited in the 14.1 simulator and previews in Xcode 12.1
struct OverlayRowClipping: View {
let rowData = (1...50).map { "row \($0)" }
@State var alertIsOpen = false
var body: some View {
List {
Section(header: Text("The Header")) {
View isBidirectional.swift
func testIsBidirectional() {
func assert<C: Collection>(_ collection: C, isBidirectional: Bool) {
XCTAssertEqual(collection.isBidirectional, isBidirectional)
assert([1, 2, 3], isBidirectional: true)
assert(Set([1, 2, 3]), isBidirectional: false)
extension Collection {
View areEquatablyEqual.swift
/// - returns: `true` when dynamic type is `Equatable` and `==` returns `true`, otherwise `false`.
func areEquatablyEqual(_ lhs: Any, _ rhs: Any) -> Bool {
func receiveLHS<LHS>(_ typedLHS: LHS) -> Bool {
let rhsAsLHS = rhs as? LHS
else { return false }
return areEquatablyEqual(typedLHS, rhsAsLHS)
return _openExistential(lhs, do: receiveLHS)
anandabits / Catamorphism.swift
Created Jun 27, 2019
An implementation of the catamorphism recursion scheme in Swift
View Catamorphism.swift
// NOTE: This code was written when I first figured out how to encode HKT in Swift.
// There is a lot that can be improved and I would write it somewhat differently today.
// This example shows how higher-kinded types can be emulated in Swift today.
// It acheives correct typing at the cost of some boilerplate, manual lifting and an existential representation.
// The technique below was directly inspired by the paper Lightweight Higher-Kinded Polymorphism
// by Jeremy Yallop and Leo White found at
/// `ConstructorTag` represents a type constructor.
/// `Argument` represents an argument to the type constructor.
anandabits / Safer SwiftUI
Last active Nov 8, 2020
Towards a safer SwiftUI environment
View Safer SwiftUI

Towards a safer SwiftUI environment

Swift UI's @EnvironmentObject is currently prone to runtime errors. If a view uses an environment object of a type that was not injected using environmentObject a fatalError occurs. This document sketches a design that would support compile-time checking of environment object usage. It requires a few language enhancements.

Tuple intersection types

Swift's protocol composition types such as Protocol1 & Protocol2 are a form of intersection types. Other forms of intersection types are possible. For example, Flow has object intersection types. Tuple intersection types for Swift would be very similar to these.

Below, you can see the examples in the Flow documentation converted to Swift's tuples:

anandabits /
Last active Jul 2, 2019
Identifiable proposal



SwiftUI introduces an Identifiable protocol. This concept is broadly useful—

anandabits / Identifiable.swift
Last active Nov 2, 2020
Implementation of the Swift Identifiable protocol
View Identifiable.swift
/// A class of types whose instances hold the value of an entity with stable identity.
protocol Identifiable {
/// A type representing the stable identity of the entity associated with `self`.
associatedtype ID: Hashable
/// The stable identity of the entity associated with `self`.
var id: ID { get }
anandabits /
Last active Apr 11, 2019
Enhanced Variadic Parameters

Enhanced Variadic Parameters


This proposal enhances variadic parameters by introducing support for user-defined types, labeled variadic parameters, and a choice at the call site of whether to provide a variadic argument list or a collection value.

anandabits /
Last active Apr 10, 2019
Explicit Memberwise Initializers

Explicit Memberwise Initialization