| /*: | |
| 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. |
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 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.
| <!-- | |
| 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 - |
| // 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 |
| 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 |
| // https://twitter.com/BelleBCooper/status/1192173933983715328 | |
| import Combine | |
| import Foundation | |
| import PlaygroundSupport | |
| PlaygroundPage.current.needsIndefiniteExecution = true | |
| /// JSON format: | |
| /// |
| precedencegroup XByYPrecedence { | |
| associativity: left | |
| higherThan: MultiplicationPrecedence | |
| } | |
| infix operator ×: XByYPrecedence // U+00D7 MULTIPLICATION SIGN | |
| // ------ | |
| import CoreGraphics |
| import SwiftUI | |
| func `let`<Value, Return>(_ expression: Value, body: (Value) -> Return) -> Return { | |
| body(expression) | |
| } | |
| struct ContentView: View { | |
| var body: some View { | |
| GeometryReader { geometry in | |
| `let`(geometry.size.width / 2) { lineWidth in |
| import Dispatch | |
| import PlaygroundSupport | |
| @propertyDelegate | |
| struct Atomic<A> { | |
| private var _value: A | |
| private let queue = DispatchQueue(label: "property wrapper") | |
| init(initialValue: A) { | |
| _value = initialValue |
