Building Reactive Applications With Combine

Episode 1



Welcome to Building Reactive Applications With Combine. As the name suggests, this series zooms in on Apple's Combine framework. We cover the the ins and outs of the framework and you learn everything you need to know to make your projects reactive with the Combine framework.

Episode 2

What Is Reactive Programming


Combine is sometimes referred to as a functional reactive programming framework, but that isn’t correct. It is more accurate to describe Combine as a reactive programming framework that uses functional programming techniques.

Episode 3

First-Class Functions and Function Types


Swift isn't a functional programming language, but it does have a number of functional features. The Combine framework relies on these functional features so it is important that you understand the basics of functional programming. That is the focus of this and the next episode.

Episode 4

Pure Functions and Higher-Order Functions


In the previous episode, you learned about function types and what it means for Swift to have first-class functions. With these concepts in mind, we continue exploring the functional features of the Swift programming language. In this episode, we explore pure functions and higher-order functions. We start with pure functions.

Episode 5

What Is Combine


Earlier in this series, we defined reactive programming as working with asynchronous streams of data. Now that you know what asynchronous streams of data are, it is clear why asynchronous programming is such a powerful concept.

Episode 6 Plus

Getting Your Feet Wet With Combine


It is time to show you what Combine feels like and what it can do for you. What do you gain by using the Combine framework in your projects? Let's start with some good news. The Combine framework has a relatively small vocabulary. You don't need to spend days or weeks familiarizing yourself with a plethora of types, protocols, and terminology.

Episode 7 Plus

Managing Subscriptions


In the previous episode, you learned about publishers and subscribers. Combine creates a subscription when a subscriber is attached to a publisher. In the setupNotificationHandling() method of the RootViewModel class, the subscription is returned to the view model as an AnyCancellable instance. The view model holds on to the AnyCancellable instance to prevent the subscription from terminating early. We covered this in the previous episode.

Episode 8 Plus

Adding Operators to the Mix


We haven't simplified or improved the implementation of the setupNotificationHandling() method of the RootViewModel class by adding Combine to the mix. In fact, Combine introduced additional complexity and we now need to manage the subscriptions we create. It is true that Combine comes with a bit of overhead. The traditional Cocoa API seems to be the better choice. Right?

Episode 9 Plus

Working With Publishers and Subscribers


Streams of values are at the heart of reactive programming. These values are delivered by publishers. In this episode, we zoom in on the relationship between publishers and subscribers.

Episode 10 Plus

Understanding the Life Cycle of a Subscription


You learned in the previous episode that a publisher sends zero or more values. A publisher emits an error if something goes wrong and, if the publisher is finite, it can send a completion event. In this episode, we continue exploring the relationship between publishers and subscribers. We zoom in on the life cycle of a subscription.

Episode 11 Plus

Reactifying Swift with the Published Property Wrapper


The Cocoa frameworks use a range of asynchronous interfaces, including the target-action pattern, key-value observing, notifications, and callbacks. We can leverage the Combine framework to create a single, unified interface for asynchronous programming. This opens up a number of compelling advantages.

Episode 12 Plus

Filtering and Transforming Elements with Operators


The Published property wrapper lowers the barrier to start integrating the Combine framework into a project. There are a few details you need to take into account, though. Remember from the previous episode that we need to address two issues. Let's look at the first issue.

Episode 13 Plus

Using Publishers to Push Data


We made good progress in the previous episodes, but we need to make some changes to the RootViewController and RootViewModel classes. We address three issues in this episode. First, the RootViewController class shouldn't be aware of CLLocation objects. Second, the RootViewModel class should expose a publisher that emits weather data. Third, we need to restore the pull-to-refresh feature. Let's get started.

Episode 14 Plus

Hiding Implementation Details with Type Erasure


The root view controller displays the weather data the publisher emits. Every time the publisher emits weather data, the child view controllers of the root view controller receive the weather data and display it to the user. This works fine, but we can make it more reactive.

Episode 16 Plus

Bridging Imperative and Reactive Programming


There are a few user interface issues we need to address in this episode. The day view controller no longer shows its activity indicator view while it is waiting for weather data and the user interface elements that show the weather data should only be shown when there is weather data to display. Let's find out how we can resolve these issues.