withEligibility

withEligibility is a software design pattern and a common utility in codebases used to conditionally execute a block of logic based on an eligibility check. The core idea is to separate eligibility verification from business logic by wrapping a computation with a predicate that determines whether the caller or data meets predefined criteria. This approach promotes modularity, reuse, and consistent validation across an application.

In practice, withEligibility typically takes a predicate or set of requirements and an action to perform if those requirements are met. If the eligibility criteria are satisfied, the action runs and returns its result; if not, a standardized error or fallback path is produced. Implementations may support synchronous or asynchronous checks and may integrate with existing error-handling and logging facilities. Some designs use a result type or option type to clearly communicate success or failure without exceptions.

Common variants include predicate-based checks (role, permission, or attribute requirements), data-driven validations (eligibility determined by input data), and gateway patterns where eligibility serves as a gatekeeper before accessing resources or features. Considerations when using withEligibility include clarity of the eligibility criteria, consistency of error messaging, performance implications for expensive checks, and how to handle partial success or optimistic checks.

Related concepts include access control, authorization middleware, validation wrappers, and feature flagging. See also: authorization, validation, and error handling patterns in software design.