ServiceObject

ServiceObject is a software design pattern used to encapsulate a single business operation as a standalone object. It represents a concrete service performed by the system, coordinating domain entities, repositories, and other services to carry out a task. A service object typically exposes a simple method, such as call or execute, and contains the orchestration logic required to complete the operation. By centralizing business logic outside of models or controllers, it aims to improve maintainability, testability, and reuse.

Characteristics include a single, well-defined responsibility; a thin public interface; dependency injection of collaborators; and a predictable execution flow. Service objects are often plain objects or simple classes in dynamic languages (for example, Ruby or Python) but the pattern appears in many languages. They usually accept input via their constructor or a dedicated parameters object, perform validation, run the business steps, and return a result object or a value indicating success or failure. Error handling may be done by returning a result wrapper or by exceptions, depending on the project conventions.

Common usage patterns involve extracting nontrivial business logic from controllers or models to improve testability and to reuse logic across controllers or APIs. Variants include the use of use-case objects, interactor objects, or command objects; some projects use a service layer to aggregate several service objects. Cautions include avoiding overuse where a simple method or small class would suffice, and ensuring services remain cohesive and not overly coupled.

See also: service layer, command pattern, use-case object, interactor, PORO, repository.