vanilla-rails-delegated-types

# Delegated Types (Recording/Recordable Pattern)

A container model (Recording) unifies many content types (Recordables) that share metadata, access control, and operations.

**Core insight:** When many content types must comingle and share behavior, create a unified container rather than duplicating metadata or using complex polymorphic queries.

## When to Use

```dot
digraph decision {
    "How many content types?" [shape=diamond];
    "Do they comingle in UI?" [shape=diamond];
    "Share metadata/operations?" [shape=diamond];
    "Direct associations" [shape=box];
    "Delegated types" [shape=box];
    "Consider merging types" [shape=box];

    "How many content types?" -> "Direct associations" [label="1-2"];
    "How many content types?" -> "Do they comingle in UI?" [label="3-4"];
    "How many content types?" -> "Share metadata/operations?" [label="5+"];
    "Do they comingle in UI?" -> "Consider merging types" [label="rarely"];
    "Do they comingle in UI?" -> "Share metadata/operations?" [label="often"];
    "Share metadata/operations?" -> "Direct associations" [label="no"];
    "Share metadata/operations?" -> "Delegated types" [label="yes"];
}
```

**Use when:**
- 5+ content types (Messages, Documents, Uploads, Comments, etc.)
- Types appear together in feeds, timelines, activity streams
- Shared metadata: project, creator, timestamps, access control
- Common operations: copy, move, archive, search across all types
- Single query needed: "all content in project X sorted by date"

**Don't use when:**
- Only 1-3 types (use direct associations)
- Types are similar enough to merge (see flattening.md)
- Types don't comingle in UI
- No shared metadata or operations

## Quick Reference

| Decision | Answer |
|----------|--------|
| 1-2 content types | Direct associations |
| 3-4 types, rarely comingle | Consider merging or direct |
| 3-4 types, often comingle | Maybe delegated types |
| 5+ types, shared metadata | Delegated types |
| Only 1 type left | Flatten (se