Module specification 

Specification pattern — composable predicates over a domain type.

Useful for invariant checks, query filters, and command routing. Specifications combine with and, or, and not so complex predicates stay declarative.

struct OverThreshold(i64);
impl Specification<Order> for OverThreshold {
    fn is_satisfied_by(&self, o: &Order) -> bool { o.amount > self.0 }
}
struct InRegion(String);
impl Specification<Order> for InRegion {
    fn is_satisfied_by(&self, o: &Order) -> bool { o.region == self.0 }
}
let spec = OverThreshold(100).and(InRegion("EU".into()));
orders.iter().filter(|o| spec.is_satisfied_by(o));

Structs

AndSpec

FnSpec

Convenience: lift any Fn(&T) -> bool into a Specification.

NotSpec

OrSpec

Traits

Specification

Composable predicate over T.