ole

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)

ole

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

ole

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"

ole

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 }
    }

ole

/*:
 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.

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.

ole

A dump of the SwiftUI.framework binary for the iOS simulator (as of Xcode 12.0 beta 2) using the swift-reflection-dump tool.

Note: I used a Swift 5.3 compiler build from a few weeks ago that I had laying around. Because of ABI stability, I don't think the swift-reflection-dump version has to match the compiler version that was used to build the binary, but I'm not 100% sure.

ole

<!--
  XSLT for removing unused namespaces from an XML file.

  Author: Dimitre Novatchev
  Source: https://stackoverflow.com/a/4594626
  License: CC BY-SA, https://creativecommons.org/licenses/by-sa/2.5/

  Usage:

      xmlstarlet tr remove-unused-namespaces.xslt -

ole

// Paste into a macOS playground in Xcode and run.
// Deleting line 46 "c?.stopObserving()" triggers the assertion because
// the reference cycle caused by retaining self in the observer block is never broken.

import Foundation

let myNotification = NSNotification.Name(rawValue: "myNotification")

var cHasBeenDeallocated = false

ole

import Foundation

// MARK: - KeyedContainer

/// A property wrapper for dictionaries with keys that are raw-representable as strings.
/// It modifies the wrapped dictionary's encoding/decoding behavior such that the dictionary
/// is encoded as a dictionary (unkeyed container) rather than as an array (keyed container).
///
/// For context, see <https://oleb.net/blog/2017/12/dictionary-codable-array/>.
@propertyWrapper