mbrandonw

extension Effect {
  func cancellable<Id: Hashable>(id: Id) -> Effect<Output> {
    return Deferred { () -> PassthroughSubject<Output, Failure> in
      cancellables[id]?.cancel()
      let subject = PassthroughSubject<Output, Failure>()
      cancellables[id] = self.subscribe(subject)
      return subject
    }
    .eraseToEffect()
  }

mbrandonw

diff --git a/0084-testable-state-management-ergonomics/PrimeTime/ComposableArchitecture/ComposableArchitecture.swift b/0084-testable-state-management-ergonomics/PrimeTime/ComposableArchitecture/ComposableArchitecture.swift
index db4ab12..ab96c5f 100644
--- a/0084-testable-state-management-ergonomics/PrimeTime/ComposableArchitecture/ComposableArchitecture.swift
+++ b/0084-testable-state-management-ergonomics/PrimeTime/ComposableArchitecture/ComposableArchitecture.swift
@@ -128,3 +128,24 @@ public func logging<Value, Action>(
       }] + effects
   }
 }
+
+

mbrandonw

extension Publisher {
  func cancellable<Id: Hashable>(id: Id) -> AnyPublisher<Output, Failure> {
    return Deferred { () -> PassthroughSubject<Output, Failure> in
      cancellables[id]?.cancel()
      let subject = PassthroughSubject<Output, Failure>()
      cancellables[id] = self.subscribe(subject)
      return subject
    }
    .eraseToAnyPublisher()

mbrandonw

extension Store {
  public func send<LocalValue>(
    _ action: @escaping (LocalValue) -> Action,
    binding keyPath: KeyPath<Value, LocalValue>
  ) -> Binding<LocalValue> {
    Binding(
      get: { self.value[keyPath: keyPath] },
      set: { self.send(action($0)) }
    )
  }

mbrandonw

import Foundation

struct Parser<A> {
  let run: (inout Substring) -> A?
}

extension Parser {
  func map<B>(_ f: @escaping (A) -> B) -> Parser<B> {
    return Parser<B> { str -> B? in
      self.run(&str).map(f)

mbrandonw

func optional<A>(_ parser: Parser<A>) -> Parser<A?> {
  return Parser<A?> { str in
    .some(parser.run(&str))
  }
}

mbrandonw

extension View {
  func presentation(_ alert: Alert?) -> some View {
    guard let alert = alert else { return AnyView(self) }

    let binding = Binding<Bool>.constant(true)
    return AnyView(self.presentation(binding) { alert })
  }
}

mbrandonw

// A keypath-like structure for enums.
struct EnumKeyPath<Whole, Part> {
  // Given an enum, we can try to get the associated value in a case.
  let get: (Whole) -> Part?
  
  // Given an associated value, we can plug it into the enum.
  let set: (Part) -> Whole
}

mbrandonw

import Foundation
import PlaygroundSupport
import UIKit

class VC: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()

    self.view.backgroundColor = .white
    self.view.translatesAutoresizingMaskIntoConstraints = false

mbrandonw

func their<Root, Value>(
  _ f: @escaping (Root) -> Value,
  _ g: @escaping (Value, Value) -> Bool
  )
  -> (Root, Root)
  -> Bool {

    return { g(f($0), f($1)) }
}