Going over the basics

As a reactive framework, Combine is built upon components that publish updates (the publishers) and components that subscribe to updates (the subscribers).

In between, we’ve got the operators, which can manipulate data and control the stream flow. Let’s get an overview of Combine by starting with the publisher.

Starting with the publisher

The best way to explain how Combine works is by talking about publishers. Publishers are types that can deliver a sequence of values over time. We saw one example in Chapter 10:

URLSession.shared.dataTaskPublisher(for: url)

For a type to be a publisher, it needs to conform to the Publisher protocol, and URLSession is not the only type that does that. Timer and NotificationCenter are also types that have their publishers:

NotificationCenter.default.publisher(for:
  Notification.Name("DataValueChanged"))

Or, it can be a Timer publisher:

let timerPublisher = Timer.publish(every...