Signals a design smell indicating overuse of primitive types instead of domain‑specific objects, prompting refactoring toward richer abstractions.

Alerts developers to a modeling deficiency that encourages encapsulation of data and behavior, improving maintainability and reducing duplication.

When developers represent concepts like phone numbers, ZIP codes, monetary amounts, or dates as raw strings or numbers instead of creating dedicated value objects.

Appears in codebases where domain concepts are scattered across primitives, often seen in utility classes, DTOs, or procedural code lacking object‑oriented encapsulation.

Detect overuse of primitive types for domain concepts → extract dedicated value objects → replace primitive usages

Use of a primitive type (string, number, boolean) to represent a domain concept that lacks associated behavior.

[primitive type]

• string
• integer
• float
• phone number
• zip code
• amount
• date
• code

• Introduce Parameter Object
• Replace Data Value with Object
• Value Object

Using strings for phone numbers leading to formatting and validation bugs; using floats for monetary values causing rounding errors; scattering validation logic across the codebase.

Data Clumps (groups of primitives that always appear together), Primitive Envy (a method more interested in another object's data), Feature Envy

Do not confuse with Primitive Envy, which is a feature envy smell where a method is overly interested in another object's data.

• Data Clumps
• Primitive Obsession
• Introduce Parameter Object

Primitive Obsession is not merely about using primitives; it's about missing behavior and validation that should belong to the domain concept.

Highlights a need to refactor toward richer domain models, reducing duplication and improving type safety.

Think of a phone number stored as a plain string—should be a PhoneNumber class with formatting and validation.

Primitive Obsession often appears alongside Data Clumps; refactoring to value objects improves type safety and encapsulates validation.

Introduce Parameter Object or Replace Data Value with Object