The subscriber requests a number of elements it wants to receive.It calls receive(subscription:) on the subscriber. The publisher acknowledges the subscription request.The publisher creates a subscription by calling receive(subscriber: S) on itself.A subscriber connects to a publisher by calling subscribe(S).With some steps missing from the debug log, let’s examine the end to end life cycle: This gives us a clue about publisher-subscriber life cycle. Receive subscription: (PassthroughSubject) It prints log messages for all publishing events to console, which already can tell us a lot about the life cycle. Notice the print(_:to:) operator in the above snippet. Let subject = PassthroughSubject () let token = subject. If we cut all the extra words, Combine is this: This creates the streams of values, flowing from the input to the output. It involves chaining functions and passing values from one to the other.
Programming with Swift Combine framework is both declarative, reactive and functional. Imperative programs rely primarily on state, which is usually modified with assignments. In imperative style you write how the program works by implementing and handling a series of tasks. In declarative programming style you describe what the program does, without describing the flow of control. In Swift functions can be passed as arguments to other functions, returned from functions, stored in variables and data structures and built at run time as closures. The Reactive Manifesto tells more about it.įunctional programming is all about programming with functions.
Reactive means programming with asynchronous streams of values. It imposes functional reactive paradigm of programming, which is different from the object-oriented one that prevails in iOS development community. What is CombineĬombine is Swift declarative framework for processing values over time.
#Swift publisher 4 tutorial how to#
The goal of this article is to paint the big picture of how to use Combine framework in Swift.
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