broomburgo

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broomburgo

Answer to http://disq.us/p/1za4u75.

---

Hi, your problem is actually quite hard to solve with composition, at least without a profunctor-based approach, which is really hard to do in Swift due to the lack of higher-kinded types.

There is a solution, though, but we must be clear about what we're searching for here. In your ViewState<T> there could be no Prism that points just to T, because the inject function wouldn't know what case to produce with a value of type T: it's probably going to be an Affine.

At the bottom of this answer you'll find all the code needed to implement it: it can be directly copy-pasted into a playground.

broomburgo

protocol TaggedType {
	associatedtype TagType
}

protocol TypeConstructor1: TaggedType {
	associatedtype ParameterType1
}

protocol TypeConstructor2: TypeConstructor1 {
	associatedtype ParameterType2

broomburgo

/// source: https://broomburgo.github.io/fun-ios/post/lenses-and-prisms-in-swift-a-pragmatic-approach/

protocol LensType {
	associatedtype WholeType
	associatedtype PartType

	var get: (WholeType) -> PartType { get }
	var set: (PartType,WholeType) -> WholeType { get }

	init(get: @escaping (WholeType) -> PartType, set: @escaping (PartType,WholeType) -> WholeType)

broomburgo

feedbackModelController.deltaSignal
  .filter { $0.feedback.rawValue < $1.feedback.rawValue}
  .filter { $1.feedback == .Good || $1.feedback == .ReallyGood }
  .onReception § eachTime § inAnyCase § showThankYouAlert

broomburgo

func collectFeedbackModelChange() -> Signal<FeedbackModelChange> {
  return pageFactory.signalMakeMainPage
    .flatMap { $0.signalPolarizedChanged }
    .map(FeedbackModel.transformWithPolarized)
    + pageFactory.signalMakeSelectionPage
      .flatMap { $0.signalSelection }
      .map(FeedbackModel.transformWithFeedback)
}

broomburgo

pageFactory.signalMakeMainPage
  .flatMap { $0.signalLeaveFeedback }
  .onReception § eachTime § inAnyCase § presentSelectionPage
  
pageFactory.signalMakeSelectionPage
  .flatMap { $0.signalSelection }
  .onReception § eachTime § inAnyCase § popTopPage

broomburgo

/// MainPage initializer
init(feedbackModelController: ModelController<FeedbackModel>) {
  super.init(nibName: nil, bundle: nil)
  feedbackModelController.updateSignal.onReception § eachTime § updateViewsWithFeedbackModel
  viewReadyEmitter.signal.onReception § eachTime § feedbackModelController.notify
}

broomburgo

import Foundation

public enum Persistence {
  case Stop
  case Continue
}

public final class Signal<Subtype> {
  typealias Observation = Subtype -> Persistence

broomburgo

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface Optional : NSObject

+ (Optional*)with:(id _Nullable)value;
+ (Optional*)with:(id _Nullable)value as:(Class _Nonnull)valueClass;