design-patterns – Page 4 – Türker Yıldırım

A specification object whose two paths disagreed

NoteMarch 11, 20252 min read

A specification with an in-memory check and a query builder, both correct in isolation and disagreeing on a boundary. One character apart, and the report listed orders the…

An API versioned for the first time in six years

Deep diveMarch 6, 202514 min read

Six years of additive-only changes, and a change that cannot be additive. A field whose meaning must change, with four consumers reading it.

Tailwind 4, and the stylesheet we had already written

Deep diveFebruary 13, 20259 min read

4.0 in January, a CSS-first configuration, and a genuine reason to look again at a decision that had been made three times.

A property hook that should have stayed a method

NoteFebruary 10, 20251 min read

A get hook that looked like a property, read like a property, and issued a database query. The rule I wrote down in December — pure, cheap and…

@theme, and the custom properties we already had

NoteFebruary 4, 20252 min read

Tailwind 4 configures itself in CSS, which turns out to be the same idea as the token file we generate. The two are the same mechanism with different…

Property hooks, and the getter that was a habit

Deep diveDecember 16, 202410 min read

8.4 on 21 November, and a property can have a getter without being a method. 412 getters that return a property unchanged.

A discriminated union that the compiler narrowed for free

NoteNovember 6, 20241 min read

A result type with a literal discriminant, and every branch typed without a single assertion. The discriminant has to be a literal type on every member, and a…

An API that had two clients and three shapes

Deep diveMay 16, 202410 min read

One endpoint, two consumers, and a response that differs by header. Three serialisation paths for one resource, two of them accidental.

A constructor that validated three things and threw one exception

NoteApril 3, 20242 min read

A value object rejecting an invalid input with a message that named the type rather than the problem. One check per condition and a named constructor per failure…

An enum implementing two interfaces, and the one that was wrong

NoteMarch 18, 20242 min read

An enum implementing both a presentation interface and a domain one, which is two responsibilities agreeing to share a file. The test that settled it was asking which…