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Alex Rupérez

Published: 13 Jun 13:51
I starred sergdort/CombineFeedback at GitHub.
Unidirectional reactive architecture using new Apple Combine framework
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CombineFeedback (WIP)

Unidirectional Reactive Architecture. This is a Combine implemetation of ReactiveFeedbback and RxFeedback



Requirements for iOS apps have become huge. Our code has to manage a lot of state e.g. server responses, cached data, UI state, routing etc. Some may say that Reactive Programming can help us a lot but, in the wrong hands, it can do even more harm to your code base.

The goal of this library is to provide a simple and intuitive approach to designing reactive state machines.

Core Concepts


State is the single source of truth. It represents a state of your system and is usually a plain Swift type. Your state is immutable. The only way to transition from one State to another is to emit an Event.


Represents all possible events that can happen in your system which can cause a transition to a new State.


A Reducer is a pure function with a signature of (State, Event) -> State. While Event represents an action that results in a State change, it's actually not what causes the change. An Event is just that, a representation of the intention to transition from one state to another. What actually causes the State to change, the embodiment of the corresponding Event, is a Reducer. A Reducer is the only place where a State can be changed.


While State represents where the system is at a given time, Event represents a state change, and a Reducer is the pure function that enacts the event causing the state to change, there is not as of yet any type to decide which event should take place given a particular current state. That's the job of the Feedback. It's essentially a "processing engine", listening to changes in the current State and emitting the corresponding next events to take place. Feedbacks don't directly mutate states. Instead, they only emit events which then cause states to change in reducers.

To some extent it's like reactive Middleware in Redux having a signature of (AnyPublisher<State, Never>) -> AnyPublisher<Event, Never> allows us to observe State changes and perform some side effects based on its changes e.g if a system is in loading state we can start fetching data from network.

UI as a Feedback 🤯

This repo contains an example of UIFeedback loop inspired by the work of @Krunoslav Zaher in RxFeedback-React specifically here.

Why UI can be treated as a Feedback loop:

  • To some extent, UI is a part of the system. When the state changes we want to react to it and render new information to the user.
  • User may interact with our system by pressing buttons and views emitting Event into it
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More examples to come stay tuned 🚀