obsservable

Obsservable is a common misspelling of observable. In programming, an observable is a data source that can be observed for changes and that emits a sequence of values over time. It represents a push-based stream of data, where observers or subscribers register to receive notifications such as next values, errors, and completion signals.

Observables are typically lazy, meaning they do not start emitting until there is at least one subscriber. A subscription allows a consumer to receive values and can be disposed to stop receiving data and release resources. Many implementations provide operators that transform and combine streams, enabling functional-style data processing without mutating the source.

Key concepts include the distinction between cold and hot observables: cold observables generate values independently for each subscriber, while hot observables share a single source among subscribers. Backpressure mechanisms may be available in some implementations to control the rate of emission when downstream consumers are slower.

Common ecosystems and libraries adopt the observable pattern, notably the ReactiveX family. Examples include RxJS for JavaScript, RxJava for Java, and RxSwift for Swift. Observables are central to reactive programming, offering composable, asynchronous data flows and broad interoperability across languages and platforms.

Compared with promises, observables can emit multiple values over time and can be canceled, while promises resolve once with a single value. The observable pattern provides powerful abstractions for event streams, but it can introduce complexity and potential for resource leaks if subscriptions are not managed carefully. See also: observer pattern, reactive programming, streams, Reactive Extensions.