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Start learning the Combine framework

In this course, you will learn the basics of the Combine framework. This is for absolute beginners in functional reactive programming and Combine 🤩. You can get the full course on Combine here.

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Subscribers and Subscriptions

First I will explain how adding a subscriber like sink or assign to a publisher creates a subscription. You will learn how to cancel a subscription that means how to stop a data stream from passing values. You will also learn that passing an error 💣 will complete the data stream.

Subscribers and Subscriptions Publishers and Subjects

In the second section, you will learn about a special type of publisher that is Subjects. I will show you how to use CurrentValueSubjects and PassthroughSubjects. In SwiftUI you can also use a publisher with the property wrapper @Published. You will learn the difference between these 3 publishers and their specific use cases.

Example projects for UIkit and SwiftUI

We will also write 2 demo projects 👋 for UIKit and SwiftUI. The goal is to use Subjects and @Published to create data streams from user input. By the end of this course, you will be able to create simple data streams between different parts of your projects.

I am using MVVM to illustrate how easy it is to separate tasks into their own components. Combine is a great tool for loose communication between different components. Comparable to the Delegate pattern, closures, and observer pattern.

Course overview:

0:00 Intro

03:21 subscriptions

17:49 limited subscriptions

31:43 assign(to,on) Subscriber

40:56 assign(to,on) strong reference and memory cycle problems

46:55 assign(to) with @Published properties

52:55 multithreading with .receive(on) and subscribe(on)

01:01:36 subscription as the contract between publishers and subscribers

01:14:18 publishers

01:18:25 CurrentValueSubject

01:26:24 PassthroughSubject

01:39:42 @Published

01:49:25 Combine in SwiftUI

01:55:47 Demo project UIKit

02:12:13 Demo project SwiftUI

02:37:49 where to go from here

Resources

⬇️ download playgrounds for the course here 

📓 Resources to learn Combine here

How to go from here:

  •  convenience Publishers: Just, Future, Result, Fail, Empty https://developer.apple.com/documentation/combine 
  • Foundation: URLSession dataTask publisher, Notification center, KVO publisher
  • operators: map, tryMap, compactMap, scan, collect, append, decode https://developer.apple.com/documentation/combine/publishers-merge-publisher-operators 
  • throwing errors: Fail publisher, Future with error
  • error handling operators: catch, tryCatch, replaceError(with), assertNoFailure , mapError, setFailureType(to)
  • multithreading: Schedular protocol, receive(on), subscribe(on), batch processing with flatMap, and set number of tasks executed in parallel with flatMap(maxPublisher)
  • control resources: dropFirst, debounce, throttle, filter, removeDupicates
  • unit testing: functions that return AnyPublisher, eraseToAnyPublisher, Result.publisher
  • communication design patterns can be replaced by Combine data streams: Delegate pattern, closures, and Observer patterns

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