Combine

Combine — Foundations Skill

Purpose

Route Combine implementation tasks to the minimum required Combine Knowledge Contracts. v1 scope is the Publisher/Subscriber/sink/ AnyCancellable subscription contract, @Published/ObservableObject, PassthroughSubject/CurrentValueSubject, the core transforming/ combining operators, and assign(to:on:)/assign(to:) with cancellable lifetime management -- not async/await interop, custom conformances, backpressure, or SwiftData/Core Data interop.

Routing

Load only the contracts relevant to the task. All paths relative to knowledge/combine/.

• Subscribing with sink(receiveCompletion:receiveValue:) or sink(receiveValue:); asking whether Failure == Never applies; or reasoning about retaining/discarding an AnyCancellable -> publishers-and-subscribers.md
• Declaring @Published var x; accessing $x; conforming to ObservableObject; or asking what objectWillChange does and when it fires -> published-and-observableobject.md
• Choosing PassthroughSubject vs. CurrentValueSubject; reading or writing .value; or calling send(_:)/send(completion:) -> subjects.md
• Applying map/filter/removeDuplicates/debounce(for:scheduler:); or combining multiple publishers with combineLatest/merge/zip and asking what shape the output takes -> operators-transforming-and-combining.md
• Writing a publisher's output into a property with assign(to:on:) or into a @Published property with assign(to:); diagnosing a retain-cycle risk; or calling .store(in:) -> assign-and-memory-management.md

Never load more than the contracts relevant to the specific question.

Stop Conditions

Stop and report if the requested topic has no matching Knowledge Contract in knowledge/combine/ — do not guess or fall back to general knowledge. Combine-to-async/await interop (Publisher.values, AsyncPublisher/AsyncThrowingPublisher) is out of scope entirely -- do not fabricate a bridging pattern. Writing a custom Publisher or Subscriber conformance is out of scope entirely -- route only to the built-in publishers/operators these contracts cover. Backpressure and Subscribers.Demand reasoning is out of scope entirely -- do not fabricate demand-management guidance. Combine integration with SwiftData or Core Data is out of scope entirely -- report the boundary rather than answer from a persistence domain. Timer.publish/ NotificationCenter.publisher have no dedicated contract -- they may appear only as an example inside another contract's Compliant Example, never as their own routing target.