combine-framework

Combine enables reactive data flows by connecting publishers that emit values to subscribers that observe them. Create a publisher using Just or a Subject, apply operators like map or flatMap to transform data, then use sink to handle the results. This composes asynchronous streams without callbacks.

map transforms each value emitted by a publisher into a new value, while flatMap flattens nested publishers into a single stream. Use map for simple value transformation; use flatMap when your transformation returns a publisher itself, such as API calls or async operations.

Store subscriptions in AnyCancellable properties or a collection. When the AnyCancellable is deallocated, it automatically cancels the subscription, breaking retain cycles. This prevents publishers from holding references to subscribers indefinitely and keeps memory managed correctly.

Yes. Use @Published properties in ObservableObject classes to create publishers that SwiftUI observes automatically. Bind UI elements to these properties, and Combine handles the reactive updates when data changes, eliminating manual state synchronization.

Use merge to interleave values from multiple publishers, combineLatest to emit tuples whenever any publisher emits, or zip to pair emissions from each publisher. Choose based on whether you need all latest values, sequential pairs, or just any new value.

Use catch to handle errors and replace with a fallback publisher, retry to attempt the pipeline again on failure, or replaceError to substitute a default value. Combine lets you recover from errors without breaking the stream or crashing the app.