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Class Constructor as Convenience Interface

concept 2 connections

Design pattern used in Eventide's Useful-Objects style: the instance-level initializer is kept primitive and mechanically correct (it records raw values, its default dependencies are diagnostic substitutes), while convenience and operational concerns move to class-level factory methods like `build(user)`. The class interface (`SignUp.build(user)`) is the 'convenience' / operational interface and wires up real dependencies; the instance interface (`SignUp.new(username, password)`) is the mechanical / diagnostic interface and yields a test-friendly object with mimic defaults. Separating the two lets designers avoid mixing convenience needs into the initializer.

category
pattern
talk Doctrine of Useful Objects Separate Fact from Fiction in OOD
about
Class Constructor as Convenience Interface concept
Final refactor pairs a primitive initializer with a class-level `build` constructor to separate convenience from mechanical correctness.
concept Useful Objects
related_to
Class Constructor as Convenience Interface concept
Useful Objects separate the mechanical initializer from a class-level convenience constructor.

Provenance

Created in
Doctrine of Useful Objects — Scott Bellware at wroclove.r... 2026-04-17 22:12
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