nicklockwood

import UIKit

// Create color using P3 color space
let linearColor = UIColor(displayP3Red: 1, green: 0.5, blue: 0.2, alpha: 1)

do {
    var r: CGFloat = 0, g: CGFloat = 0, b: CGFloat = 0, a: CGFloat = 0
    linearColor.getRed(&r, green: &g, blue: &b, alpha: &a)
    print(r, g, b, a) // 1.07, 0.46, 0.0, 1.0 - not the expected values
}

nicklockwood

// Swift's untyped errors are a goddam PiTA. Here's the pattern I use to try to work around this.
// The goal is basically to try to guarantee that every throwing function in the app throws an
// ApplicationError instead of some unknown error type. We can't actually enforce this statically
// But by following this convention we can simplify error handling

enum ApplicationError: Error, CustomStringConvertible {
    
  // These are application-specific errors that may need special treatment
  case specificError1
  case specificError2(SomeType)

nicklockwood

import SwiftUI

enum OSDocumentError: Error {
    case unknownFileFormat
}

#if canImport(UIKit)

import UIKit

nicklockwood

import Foundation

// Here's a pretty typical scenario where you want to encode a polymorphic type -
// in this case a Shape type that can be either a Square or Circle. Swift provides
// a nice pattern for doing this in a type-safe way using enums:

struct Circle: Codable {
    var radius: Int
}

nicklockwood

// This gist demonstrates how you can implement versioning for a Codable struct to support loading
// old serialized data after changing the structure. Notable features of this solution:
//
// * No need to make new properties optional, or to perform post-processing on the struct after
//   loading in ordeer to populate missing values
// * No need to change the call site - from the outside this struct behaves just the same
//   as if we had implemented codable directly in the normal way.
// * Versioning can be applied individually to parents or leaves in a larger tree of
//   structs without affecting the other elements
// * This approach will work even if the original struct was not designed with versioning in mind

nicklockwood

Hacking UIView animation blocks for fun and profit

In this article, I'm going to explore a way that we can create views that implement custom Core Animation property animations in a natural way.

As we know, layers in iOS come in two flavours: Backing layers and hosted layers. The only difference between them is that the view acts as the layer delegate for its backing layer, but not for any hosted sublayers.

In order to implement the UIView transactional animation blocks, UIView disables all animations by default and then re-enables them individually as required. It does this using the actionForLayer:forKey: method.

Somewhat strangely, UIView doesn't enable animations for every property that CALayer does by default. A notable example is the layer.contents property, which is animatable by default for a hosted layer, but cannot be animated using a UIView animation block.

nicklockwood

import UIKit

extension UITextField {
    /// Add a trailing placeholder label that tracks the text as it changes
    func addTrailingPlaceholder(_ placeholder: String) {
        let label = UILabel()
        label.text = placeholder
        label.alpha = 0.3
        label.isHidden = true
        let container = UIView()

nicklockwood

/// Withable is a simple protocol to make constructing
/// and modifying objects with multiple properties
/// more pleasant (functional, chainable, point-free)
public protocol Withable {
  init()
}

public extension Withable {
  /// Construct a new instance, setting an arbitrary subset of properties
  init(with config: (inout Self) -> Void) {

nicklockwood

// ShapeScript document

detail 32

define roundedcube {
    option radius 0.25
    option size 1 1 1
    detail max(4 detail)
    define size_ size
    define diameter radius * 2 / size_

nicklockwood

/// The Jaro-Winkler edit distance between two strings (0 - 1)
func editDistance(_ lhs: String, _ rhs: String) -> Double {
    return 1 - jaroWinklerSimilarity(Array(lhs), Array(rhs))
}

/// Jaro-Winkler similarity between two strings (0 - 1)
/// https://www.geeksforgeeks.org/jaro-and-jaro-winkler-similarity/
private func jaroWinklerSimilarity(_ s1: [Character], _ s2: [Character]) -> Double {
    var jaro = jaroSimilarity(s1, s2)