Question 1

How to cancel a network request with Tomorrowland?

Accepted Answer

In the promise body, use the resolver's onRequestCancel method to observe cancellation and cancel the underlying task, such as a URLSessionTask. This ensures true cancellation, unlike simpler libraries that only flag cancellation errors.

Question 2

Tomorrowland vs PromiseKit: which is better?

Accepted Answer

Tomorrowland is better for complex workflows needing true cancellable promises and type-safe error handling, while PromiseKit is more suitable for simpler tasks with a gentler learning curve and larger community support.

Question 3

How to handle custom error types in Tomorrowland?

Accepted Answer

Define your error type and use it directly in Promise generics; for chaining promises with different errors, use .upcast to Swift.Error or leverage generic methods like flatMapError for seamless composition.

Question 4

Can I use Tomorrowland with SwiftUI?

Accepted Answer

Yes, but you must manage async state updates carefully, such as using callbacks on .main context for UI changes or integrating with Combine, as Tomorrowland doesn't provide built-in SwiftUI bindings.

Question 5

What is PromiseInvalidationToken and when should I use it?

Accepted Answer

A token that suppresses registered callbacks when invalidated, useful for UI components to avoid updating with stale data after a view is dismissed. It's distinct from cancellation and helps manage callback lifetimes efficiently.

Question 6

How to chain promises with different error types?

Accepted Answer

Use methods like flatMap that support generic errors, or convert errors to Swift.Error using .upcast for compatibility. This allows flexible chaining while maintaining type safety where possible.

Tomorrowland

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