Question 1

How do I use Signals in a Swift project?

Accepted Answer

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.

Question 2

What are the main differences between Signals and NSNotifications?

Accepted Answer

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.

Question 3

How to avoid memory leaks when using Signals?

Accepted Answer

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.

Question 4

Can Signals completely replace delegates in iOS apps?

Accepted Answer

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.

Question 5

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

Accepted Answer

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.

Question 6

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

Accepted Answer

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.

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