attac-t Skill: Casts
"Casts change storage format. Accessors change presentation."
The Decision
Use Cast when:
- Value requires different storage format (int → Money)
- Transformation applies on both read AND write
- Value Object should be reusable across models
Use Accessor when:
- Computed from other attributes
- Read-only transformation
- Depends on model state/context
The Heuristic
Ask: "Does this transform how data is stored, or how it's displayed?"
- Storage → Cast
- Display → Accessor
The Quick Test
| Ask Yourself | Answer | Use |
|---|---|---|
| Reusable across models? | Yes | Cast |
| Needs read + write? | Yes | Cast |
| Depends on other attributes? | Yes | Accessor |
| Computed value? | Yes | Accessor |
Real-World Examples
For concrete examples, see examples.md.