observablelike

Observablelike is a term used in reactive programming to describe data sources or objects that resemble an Observable but are not guaranteed to implement the full Observable interface. In practice, an observable-like value provides a stream of values over time and offers a subscribe mechanism to receive those values, errors, and completion signals. The term is often used in typing and design discussions to indicate interoperability rather than strict conformance.

Core characteristics typically include a subscribe method that accepts an observer object with optional next, error, and complete handlers, or separate callbacks. The method returns a handle—often a subscription or disposable—that can be used to cancel the subscription. Observable-like sources may be warm or cold and may vary in whether they multicast or share emissions.

Use of observablelike types supports generic composition and testing. Functions can be written to operate on any observable-like source, improving flexibility across libraries and frameworks. However, observable-like objects may lack advanced operator support, multicasting behavior, or strict sequencing guarantees found in formal Observables, so expectations should be documented.

Examples appear in typing guidelines and library adapters where a library exposes a subscribe-based API without exposing a full Observable class. By adopting an observable-like contract, code can interoperate with multiple reactive implementations while maintaining a simple, familiar interface for subscribers.