Understanding ReactiveCocoa: Core Elements, Signal Flow, Commands, and Channels

The article explains ReactiveCocoa’s core concepts—RACSignal, subscribers, cold versus hot signals, and key transformations such as bind, map, flatten and throttle—while showing how RACCommand encapsulates actions and RACChannel enables two‑way binding, together illustrating how to build expressive, maintainable data pipelines in iOS apps.

Functional Reactive ProgrammingObjective‑CRACChannel

0 likes · 25 min read

Understanding ReactiveCocoa: Core Elements, Signal Flow, Commands, and Channels

Meituan Technology Team

Aug 19, 2016 · Mobile Development

Understanding Memory Leaks with RACObserve and RACSubject in ReactiveCocoa

In ReactiveCocoa, using RACObserve inside a flattenMap or applying map to a hot RACSubject can create retain cycles because the generated blocks capture self and the subject retains its subscribers, so employing @weakify/@strongify and ensuring signals send a completed or error event breaks these hidden memory leaks.

MemoryLeakObjective‑CReactiveCocoa

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Understanding Memory Leaks with RACObserve and RACSubject in ReactiveCocoa

Meituan Technology Team

Nov 3, 2015 · Mobile Development

Understanding Cold and Hot Signals in ReactiveCocoa (RAC)

Cold signals in ReactiveCocoa emit a complete, independent sequence for each subscriber only after subscription, while hot signals continuously push shared events regardless of listeners, causing later subscribers to miss earlier values; understanding this distinction guides proper signal choice in FRP applications.

ColdSignalHotSignalObjective‑C

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Understanding Cold and Hot Signals in ReactiveCocoa (RAC)

Meituan Technology Team

Nov 3, 2015 · Mobile Development

Understanding Cold and Hot Signals in ReactiveCocoa (RAC)

Understanding ReactiveCocoa’s cold and hot signals reveals that each subscription to a cold fetchData signal triggers a separate network request, causing duplicated calls, while converting the signal to hot with shareReplay or publish ensures a single request is shared across UI bindings and error handling.

ColdSignalHotSignalObjective‑C

0 likes · 11 min read

Meituan Technology Team

Nov 3, 2015 · Mobile Development

Understanding Hot and Cold Signals in ReactiveCocoa (RAC)

The article explains that in ReactiveCocoa cold signals are plain RACSignal instances that start their work per subscriber, while hot signals are RACSubject (or subclasses) that broadcast a single execution to all observers, and demonstrates converting cold to hot using subjects, multicast operators, and replay helpers such as replayLazily to share network requests.

ColdSignalFunctionalReactiveProgrammingHotSignal

0 likes · 18 min read

Understanding Hot and Cold Signals in ReactiveCocoa (RAC)

Meituan Technology Team

Jul 16, 2015 · Mobile Development

Understanding RACSignal Subscription, Multicast, and Replay in ReactiveCocoa

The article breaks down RACSignal’s three‑step subscription flow, then explains how multicast and replay operators—built on RACSubject and RACReplaySubject—share a single source, buffer values, and ensure side‑effects like network requests execute only once regardless of how many subscribers attach.

Objective‑CRACSignalReactiveCocoa

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Understanding RACSignal Subscription, Multicast, and Replay in ReactiveCocoa