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Combine in iOS - Basics
- 1. Introduction of Apple’s exciting new framework Combine
- 2. Imperative vs Declarative Telling the machine how to do something and as a result what you want to happen will happen. Telling a machine what would like to happen and let the computer figure how to do it!
- 4. Async in Swift Grand Central Dispatch NSOperationQueue POSIX Threads Target / Action Callbacks / Completion Handlers
- 5. Some factors about async in swift Hard to understand More manual effort Callback hell Hard to maintain
- 6. Reactive Programming, which focuses on asynchronous data streams, which you can listen to and react accordingly. Functional Programming, which emphasizes calculations via mathematical-style functions, immutability and expressiveness, and minimizes the use of variables and state. FRP is the combination of functional and reactive paradigms. In other words, it is reacting to data streams using the functional paradigm. Eg: RxSwift, ReactiveSwift Functional Reactive Programming
- 7. What is Combine? Combine is a new reactive framework created by Apple that streamlines how you can process asynchronous operations. Combine code is declarative and succinct, making it easy to write and read once you have a basic understanding of it. Combine also allows you to neatly organize related code in one place instead of having that code spread out across multiple files.
- 8. Publisher The essence of Combine is: publishers send values to subscribers. To become a publisher, a type must adopt and conform to the Publisher protocol, which includes the following: associatedtype Output associatedtype Failure : Error Specifically, a publisher must define the type of values it will send, and its failure error type or Never if it will never send an error.
- 9. How to create publishers Combine is integrated throughout the iOS SDK and Swift standard library. For example, this enables us to create a publisher from a NotificationCenter.Notification, or even an array of primitive values.
- 10. Subscriber A subscriber attaches to a publisher to receive values from it. And the process is called Subscription. Subscribers must adopt and conform to the Subscriber protocol, which includes the following: associatedtype Input associatedtype Failure: Error
- 11. How to create subscription There are two ways to create a subscription to a publisher: ● By using one of the sink operators. ● By using one of the assign(to:on:) operators.
- 12. Example Usecase 1 Chaining Asynchronous Calls
- 13. Example Usecase 2 Performing Multiple Asynchronous Calls
- 14. Example Usecase 3 Merges Two Notifications and maps them
- 15. How to stop subscriptions There are two ways to stop subscriptions: ● Call cancel() on a subscription token. ● Do nothing and let normal memory management rules to apply, i.e., the token or collection of AnyCancellable will call cancel() on the subscriptions upon deinitialization.
- 17. Major advantages Combine is integrated into many existing frameworks in iOS, macOS, watchOS, and tvOS. SwiftUI that relies heavily on Combine. The Foundation framework contains a lot of extensions to work with Combine. It allows to work with common types we are already familiar with: ● A URLSessionTask Publisher that publishes the data response or request error ● Operators for easy JSON decoding ● A Publisher for a specific Notification.Name that publishes the notification
- 18. Combine Combine Deployment Target iOS 13.0+ Platforms supported iOS, macOS, tvOS, watchOS Spec Reactive Streams (+ adjustments) Framework Consumption First-party (built-in) Maintained by Apple UI Bindings SwiftUI
- 19. Thank you
Editor's Notes
- #7: Observer pattern Powerful operators Light and Switch
- #8: 3 things in combine: Publisher, Subscriber and Operators
- #10: We can create our own custom publisher types by adopting and conforming to the Publisher protocol. However there are two Publisher types that will most often suit your needs without having to define a custom publisher: PassthroughSubject and CurrentValueSubject.
- #11: A subscriber can only have one subscription
- #12: Sink The sink operators include closure parameters to handle values or a completion event received from a publisher. Assign assign method of Combine to bind a stream to a key path and therefore connect it to the properties of a view, but there is no way to get any stream from UI components.
- #14: Usually, when we want to wait for two asynchronous operations to finish in order to perform a task, we have to use DispatchGroups and to do manual management. With Combine Swift, we can simply use zip operator explained form above.
- #15: Merges Two Keyboard Notifications and maps them into current keyboard height. After that, it uses the height to assign to scroll view content insets.
- #18: A URLSessionTask Publisher that publishes the data response or request error Operators for easy JSON decoding A Publisher for a specific Notification.Name that publishes the notification
- #19: Have to wait for some time.