Specification Pattern

ELI5 — The Vibe Check

The specification pattern turns business rules into reusable, composable objects. Instead of if-statements scattered everywhere, you create specs like 'IsActive', 'HasPremiumPlan', 'CreatedThisMonth' and combine them with AND, OR, NOT. It's like building filters from LEGO blocks.

Real Talk

The specification pattern encapsulates business rules as first-class objects that can be combined using boolean logic (AND, OR, NOT). Each specification implements a single rule with an isSatisfiedBy method. Specifications can be used for validation, querying, and filtering while keeping business logic DRY and domain-expressive.

Show Me The Code

class IsActive {
  isSatisfiedBy(user: User) { return user.status === 'active'; }
}
class HasPremiumPlan {
  isSatisfiedBy(user: User) { return user.plan === 'premium'; }
}

const canAccessFeature = new AndSpec(new IsActive(), new HasPremiumPlan());
if (canAccessFeature.isSatisfiedBy(user)) { /* grant access */ }

When You'll Hear This

"Compose specifications to build complex business rules from simple building blocks." / "The specification pattern keeps our eligibility logic testable and reusable."