Paano mo modipikasyon domain menyang kelas sing dirancang kanthi apik?

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Pemodelan kelas sing apik tegese kelas sing peta menyang konsep domain sing nyata, saben-saben kanthi **siji tanggung jawab sing jelas**, ana hubungan **is-a/has-a** sing jujur, lan gumantung ing **abstraksi** ing wates. Ora ana rumus, nanging ana proses sing bisa diulang. ## Proses praktis ```text 1. Find the NOUNS → candidate classes (Order, Customer, Payment) 2. Find the VERBS → candidate behaviors/methods (place, refund, ship) 3. Assign each behavior to the class that OWNS the data it needs (high cohesion) 4. Choose relationships: IS-A (rare, must pass LSP) vs HAS-A (default) 5. Depend on interfaces at boundaries (DIP); inject volatile dependencies 6. Keep invariants inside the object (encapsulation); prefer immutability for values ``` ## Perilaku ngetung data ```java // ❌ logic separated from data (anemic) → low cohesion class Order { List items; } class OrderCalculator { double total(Order o) {...} } // ✅ behavior lives with the data it operates on class Order { private final List items; public Money total() { // owns its own rule return items.stream().map(Item::price).reduce(Money.ZERO, Money::plus); } } ``` ## Heuristik sing njaga hirarki sehat | Heuristik | Alasan | |---|---| | Luwih seneng komposisi; gunakake warisan mung kanggo is-a sing bener | Nyegah jebakan base class sing rapuh / LSP | | Tetep hirarki cethak (2–3 level) | Wit jero ngubungake kabeh | | Siji alasan kanggo owah saben kelas (SRP) | Lokalisir owahan | | Program menyang interface ing jahitan | Testabilitas, ketukaran | | Gawe value objects immutable | Ilangake kelas bug | ## Jebakan Ora modipikasyon *kabeh* donya maju. Mulai cilik kanthi kelas konkret; ekstrak abstraksi mung nalika variasi nyata katon (aturan telu). Hirarki spekulatif tuwa kanthi ala. ## Dene iku penting Model sing cerminan domain nggawe kode tetenger dhewe — insinyur anyar maca `order.refund()` lan ngerti bisnis, ora mung sintaks. Penolakan ketemu: kelas kohesif, cendhela cilik lokalisir owahan, dadi fitur lan perbaikan bug tutul sawetara berkas tinimbang mribik ing sistem.

Heuristik	Alasan
Luwih seneng komposisi; gunakake warisan mung kanggo is-a sing bener	Nyegah jebakan base class sing rapuh / LSP
Tetep hirarki cethak (2–3 level)	Wit jero ngubungake kabeh
Siji alasan kanggo owah saben kelas (SRP)	Lokalisir owahan
Program menyang interface ing jahitan	Testabilitas, ketukaran
Gawe value objects immutable	Ilangake kelas bug