`collect()` is a powerful operator that enables us to receive all at once the outputs from a publisher. It collects all received elements, and emits a single array of the collection when the upstream publisher finishes. [0, 1, 2, 3].publisher .sink { (output) in print(output) }.store(in: &subscriptions) The publisher will…

SwiftUI enables us to access common pieces of information throughout the app using `@Environment` objects avoiding the cumbersomeness of passing data through the views. There are many built-in environments such as `openURL`, `colorScheme` or `managedObjectContext` to manage data storage with Core Data. All these environments are defined in the Swift…

While creating a custom operator out of Combine’s built-in ones in the `Publisher` extension is a useful (and quick!) technique to harmonize some common reactive behaviors, it is sometimes necessary to provide with some more in-depth customization to achieve our goal. Combine enables us to conform to the `Publisher`, `Subscription`…

Property wrappers are one of Swift’s major new features enabling us to attach some specific behavior each time a property gets accessed or mutated. It comes in very handy when one needs to encapsulate some common logic such as the user defaults which are often read and written to throughout…

While Combine provides with a `sink` method that conveniently « creates the subscriber and immediately requests an unlimited number of values, prior to returning the subscriber. », the framework also enables us to define our own subscriber by conforming to the `Subscriber` protocol. — Use case class CustomSubscriber: Subscriber {…

Functions, in Swift, are first-class citizens that can be passed as arguments, stored in properties or returned from functions. When dealing with Swift built-in functions such as `map` and `forEach`, one often ends up using the trailing closure syntax to provide with the required behavior. let stackView = UIStackView() let views…

Combine is designed around structs — which are value types — ensuring that a copy is made by the system whenever a resource is stored in a property (or passed around in functions) so it can deliver values without side-effects. extension Publishers { /// A publisher that publishes a given…

switchToLatest() is one of the most powerful operator in Combine as it enables to switch entire publisher subscriptions on the fly while canceling the pending publisher subscription, thus switching to the latest one. Only publishers that emit publishers can use the `switchToLatest()` operator. AnyPublisher<AnyPublisher<[Post], Never>, Never> Every time a publisher…

While Combine doesn’t provide a built-in API to handle UIKit’s gestures yet, the Publisher and Subscription protocols give us the ability to create our own solution. — Creating a custom publisher First, let’s create a custom publisher by conforming to the Publisher protocol which is composed of two associated types namely Output and Failure. `Output`…