Whenever a new blog post is “Published”, the label “Subscriber” will update its text value. Last post is: Getting started with the Combine framework in Swift Print("Last post is: \(lastPostLabel.text!)") Let blogPost = BlogPost(title: "Getting started with the Combine framework in Swift", url: URL(string: "")!) This will result in the following complete code example: import UIKitīlogPostPublisher.subscribe(lastPostLabelSubscriber) Return (notification.object as? BlogPost)?.title ? "" let blogPostPublisher = NotificationCenter.Publisher(center. Using this operator, we can change the output value from a Notification to the required String? type. Therefore, we need to use an operator you might be familiar with already: map. The text property of the label requires receiving a String? value while the stream publishes a Notification. Instance method ‘subscribe’ requires the types ‘’ (aka ‘Notification’) and ‘String?’ be equivalent Trying out this code you might already notice that this doesn’t work yet. The label is now a “Subscriber” to the notification “Publisher” and waits for new values to process. Let lastPostLabelSubscriber = Subscribers.Assign(object: lastPostLabel, keyPath: \.text) We could, for example, create a lastPostTitleLabel which subscribes to the publisher. However, this will only happen as soon as there is a subscriber. This publisher will listen for incoming notifications for the newBlogPost notification name. Let blogPostPublisher = NotificationCenter.Publisher(center. Static let newBlogPost = Notification.Name("new_blog_post") In the following code example, we create a new Publisher for our new blog post notification. Taking the last example, we can explain the concept of a Publisher and a Subscriber. A Publisher for a specific Notification.Name that publishes the notification.A URLSessionTask Publisher that publishes the data response or request error.It allows you to use Publishers from common types you’re already familiar with. The Foundation framework contains a lot of extensions to work with Combine. Keep this in mind while we go over some Publishers’ examples in the Foundation framework while working with Combine. A Publisher exposes values that can change on which a subscriber subscribes to receive all those updates. If you’re familiar with RxSwift:ĭifferent namings, but they both give the same understanding. The Combine framework comes with so-called Publishers and subscribers. This will help you to understand better how the code works and behaves. Before we dive straight into the code examples, it’s better to start with some background information. The basic principles of Combine make you understand how it works and how you can use it. I want to map it’s data to a JSON model.In other words, a FRP sequence could be described as follows: Examples of these kinds of values include network responses, user interface events, and other types of asynchronous data. Functional Reactive Programming (FRP) languages allow you to process values over time. It allows you to write functional reactive code by providing a declarative Swift API. You can compare the Combine framework to frameworks like RxSwift and ReactiveSwift (formally known as ReactiveCocoa). Hopefully, after reading this blog post, you should be able to answer the above questions, and you’re able to understand what Combine can do. What does it actually mean? What can I do with it, and when should I use it?Īpple describes the framework as follows:Ĭustomize handling of asynchronous events by combining event-processing operators. Get started for free.Īt first, “processing values over time” might sound quite overwhelming. That’s the reason why we need to tell our method the type we expect.In-App Purchases Made Easy With a few lines of code, RevenueCat gives you everything you need to build, analyze, and grow in-app purchases and subscriptions without managing servers or writing backend code. Observe the last two lines, our method is returning a Starship and then a SpaceStation. struct Starship: Codable let enterprise = Starship(name: "Enterprise D", captain: "Jean Luc Picard") let deepSpace9 = SpaceStation(name: "Deep Space Nine") (value: enterprise, forKey: "enterprise") (value: deepSpace9, forKey: "deepSpace9") let value0: Starship? = (forKey: "enterprise") let value1: SpaceStation? = (forKey: "deepSpace9") Let’s say we have a Starship struct which conforms to Codable. If you are an iOS developer, there’s a good chance you have used UserDefaults in the past to save and load local data.Ĭurrently, UserDefaults supports the following data types: - URL - Any (NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary) - Bool - Double - Float - Int - String Ok, but what about Codable? ? Adding Codable support to UserDefaults with Swift
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