How do I use Signals in a Swift project?

You need to create concrete sub-classes using the CreateSignalInterface and CreateSignalImplementation macros for each signal type, as described in the Swift support section. This adds boilerplate compared to Objective-C but ensures type safety in Swift code.

What are the main differences between Signals and NSNotifications?

Signals offers compile-time type safety, automatic observer lifecycle management, and inline callbacks, whereas NSNotifications are error-prone with runtime crashes, lack type safety, and require manual de-registration. Signals is designed to address these NSNotification pitfalls directly.

How to avoid memory leaks when using Signals?

Signals automatically weakifies self in callbacks to prevent retain cycles, and observers manage their own deallocation. However, ensure you cancel observers if needed manually, as shown in the cancellation example, to handle complex scenarios.

Can Signals completely replace delegates in iOS apps?

Yes, for cases where no return data is needed from observers, as noted in the introduction. Signals provides a cleaner, inline alternative, but delegates might still be preferable for bidirectional communication or when adhering to Apple's design patterns.

Signals vs Combine: which should I use for new iOS projects?

Signals is better for Objective-C-heavy codebases needing simple, type-safe eventing, while Combine is native to Swift and integrates seamlessly with SwiftUI. For Swift-first projects, Combine offers more features and better performance, but Signals excels in legacy Objective-C environments.

How to set up a one-time observer with Signals?

Set the cancelsAfterNextFire property to YES on the returned UBSignalObserver, as shown in the advanced usage section. This automatically cancels the observer after it fires once, simplifying ephemeral event handling.

signals-ios — Type-Safe Eventing for iOS

What is signals-ios?

Signals is an eventing library for iOS that enables type-safe implementation of the Observable pattern. It replaces error-prone NSNotifications and cumbersome delegates with a system that ensures compile-time safety and reduces boilerplate code. The library allows objects to fire events and other objects to observe them with inline callbacks, automatically managing observer lifecycles.

Target Audience

iOS developers building applications in Objective-C or Swift who need a robust, type-safe alternative to NSNotifications or delegates for event communication between components.

Value Proposition

Developers choose Signals for its compile-time type safety, which prevents common runtime crashes associated with NSNotifications, and its attach-and-forget observation that simplifies memory management. It offers a more declarative and less error-prone way to handle events compared to traditional iOS patterns.

Typeful eventing

Use Cases

Best For

Implementing type-safe event communication between view controllers and models
Replacing NSNotifications to avoid runtime crashes from data type mismatches
Simplifying delegate patterns when no return data is needed
Managing network request callbacks with multiple observers
Handling user interface updates from background tasks safely
Building modular iOS apps with decoupled component interactions

Not Ideal For

Swift-only projects preferring native Combine or SwiftUI observation for seamless integration
Cross-platform development needing eventing that works beyond iOS (e.g., with Android or web)
Teams already using reactive libraries like RxSwift which offer more operators and a broader ecosystem
Applications with minimal event communication where lightweight closures or delegates suffice without dependency overhead

Pros & Cons

Pros

Compile-Time Type Safety

Ensures data type mismatches are caught at compile time, preventing runtime crashes common with NSNotifications, as highlighted in the README's critique of NSNotification pitfalls.

Automatic Lifecycle Management

Observers self-manage deallocation with attach-and-forget observation, reducing memory leak risks without manual de-registration, a key improvement over NSNotifications.

Flexible Observation Behavior

Supports one-time observation, custom callback queues, and firing previous data, allowing fine-tuned control for advanced use cases as demonstrated in the advanced usage section.

High Reliability Assurance

Backed by comprehensive unit test coverage noted in features, ensuring stability across diverse scenarios and reducing bug potential in event-driven code.

Cons

Cumbersome Swift Integration

Swift usage requires creating concrete sub-classes with macros like CreateSignalInterface, adding boilerplate and complexity compared to native Swift eventing solutions, as admitted in the Swift support section.

Limited Observer Capacity

Default max of 100 observers per signal can NSAssert in high-volume scenarios, forcing manual adjustments via maxObservers property, which adds overhead for legitimate use cases.

Objective-C Centric Design

Primarily built for Objective-C with protocol-based signals, making it less idiomatic for modern Swift-first development and requiring extra steps for type safety in Swift.

Frequently Asked Questions

What is signals-ios?

Target Audience

iOS developers building applications in Objective-C or Swift who need a robust, type-safe alternative to NSNotifications or delegates for event communication between components.

Value Proposition

Use Cases

Best For

Implementing type-safe event communication between view controllers and models
Replacing NSNotifications to avoid runtime crashes from data type mismatches
Simplifying delegate patterns when no return data is needed
Managing network request callbacks with multiple observers
Handling user interface updates from background tasks safely
Building modular iOS apps with decoupled component interactions

Not Ideal For

Swift-only projects preferring native Combine or SwiftUI observation for seamless integration
Cross-platform development needing eventing that works beyond iOS (e.g., with Android or web)
Teams already using reactive libraries like RxSwift which offer more operators and a broader ecosystem
Applications with minimal event communication where lightweight closures or delegates suffice without dependency overhead

Pros & Cons

Pros

Compile-Time Type Safety

Ensures data type mismatches are caught at compile time, preventing runtime crashes common with NSNotifications, as highlighted in the README's critique of NSNotification pitfalls.

Automatic Lifecycle Management

Observers self-manage deallocation with attach-and-forget observation, reducing memory leak risks without manual de-registration, a key improvement over NSNotifications.

Flexible Observation Behavior

Supports one-time observation, custom callback queues, and firing previous data, allowing fine-tuned control for advanced use cases as demonstrated in the advanced usage section.

High Reliability Assurance

Backed by comprehensive unit test coverage noted in features, ensuring stability across diverse scenarios and reducing bug potential in event-driven code.

Cons

Cumbersome Swift Integration

Limited Observer Capacity

Default max of 100 observers per signal can NSAssert in high-volume scenarios, forcing manual adjustments via maxObservers property, which adds overhead for legitimate use cases.

Objective-C Centric Design

Primarily built for Objective-C with protocol-based signals, making it less idiomatic for modern Swift-first development and requiring extra steps for type safety in Swift.

Frequently Asked Questions

signals-ios

What is signals-ios?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?

signals-ios

What is signals-ios?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?