SwiftUI Combine Essentials: Everything You Need to Know!

In modern iOS development, Combine and SwiftUI have become essential for building reactive and efficient user interfaces. Combine, Apple’s framework for handling asynchronous events and data streams, works seamlessly with SwiftUI, enabling developers to manage data flow and UI updates with minimal code. This combination offers a more declarative and reactive approach to app development, which reduces the need for manual synchronization and complex callback patterns.

Understanding the most frequently used commands in Combine is key to making the most of this framework. From publishers that emit values to operators that transform data and subscribers that handle results, these commands allow us to handle complex event sequences in a clear, concise, and highly efficient way. In this article, we’ll explore some of the most important Combine commands, helping you build robust and responsive SwiftUI applications with confidence.

Here’s a list of some of the most important and frequently used commands in SwiftUI’s Combine framework, focusing on publishers, operators, and subscribers:

1. Publishers
   • Just: Creates a publisher that emits a single value and then completes.
   • Publishers.Sequence: Converts a sequence, such as an array, into a publisher.
   • PassthroughSubject: A subject that broadcasts values to any subscriber, ideal for bridging non-Combine code.
   • CurrentValueSubject: Holds a current value that can be updated and observed, often used for state.
   • Deferred: Delays the creation of the publisher until a subscriber subscribes.
2. Operators
   • map: Transforms the output of a publisher.
   • flatMap: Transforms each element from one publisher into another publisher.
   • filter: Filters values based on a condition.
   • removeDuplicates: Filters out duplicate values.
   • compactMap: Transforms elements, removing any nil values from the sequence.
   • scan: Accumulates a value over time, similar to a reduce function but emits intermediate states.
   • debounce: Delays values until a specific time interval has passed without another emission.
   • throttle: Limits the rate at which values are emitted.
   • merge: Combines multiple publishers into one, emitting values from any of the publishers.
   • combineLatest: Combines the latest values from multiple publishers.
   • zip: Combines values from multiple publishers in pairs.
   • catch: Handles errors by replacing the publisher with another publisher.
   • retry: Retries a failed publisher a specified number of times.
   • replaceError: Replaces errors with a specified output.
3. Subscribers
   • sink: Attaches a subscriber to receive values and completion events, commonly used for side effects.
   • assign: Assigns a received value to a property on an object.
   • AnyCancellable: Stores a subscription, which can be used to cancel the subscription later.
4. Other Commonly Used Concepts
   • CombineLatest: Combines multiple publishers into one.
   • Subjects: Used for bridging non-Combine code or triggering manual events.
   • Schedulers: Manages the execution of publishers on specific queues or threads, such as DispatchQueue.main.

These commands and operators cover most of the core functionality in SwiftUI Combine, helping you manage asynchronous events and data transformations effectively.

Check the repository that demonstrates those commands

https://github.com/san0suke/swift-ui-combine2