Is Your Inheritance a Design Model—or Just a Field Merger?¶
Type: Structure
Category: Domain
Audience: Anyone who thinks "extends" means "understands"
🔍 Why This Matters¶
Inheritance looks like reuse.
But in systems, it’s often just a silent entanglement.
Used wrong, inheritance isn’t a structure—it’s a trapdoor.
⚠️ Danger Signs¶
- A subclass exists, but adds no real behavior—just fields
- Parent and child differ in validation rules
- Removing the parent breaks half the unrelated services
- You're not sure what the subtype means, just that it shares some columns
✅ Better Structures¶
- Use composition unless the subtype behaves differently
- If two models share shape but not meaning, keep them separate
- Make inheritance explicit at the behavior level (
execute(),isAllowed()) - Document: “why does this extend that?”
🧠 Real Question¶
Does this inheritance reflect shared semantics—or just data gravity?
Are you modeling a reality, or avoiding effort?
❓ FAQ¶
-
Q: But the shape is the same. Isn’t reuse natural?
A: The shape is irrelevant. The meaning isn’t. -
Q: Should I always avoid inheritance?
A: No. Just don’t use it because your ORM makes it easy.