ArjanCodes
30 minutes
Specification Pattern in Python using Generics and Decorators
The specification pattern, originating in domain-driven design, encapsulates business rules as small, named, composable units that can be combined with boolean logic (and, or, not) and reused across a codebase, separating the definition of a rule from its evaluation. In a functional style, a rule is a predicate (a function returning true or false) wrapped in an object that overloads logical operators so rules can be composed without being executed, and generics allow such rules to apply to any domain type. This belongs to software design patterns and domain modeling, and it enables business rules to be centralized, reusable, and ultimately expressed as data, at the cost of potential over-engineering.