> ## Documentation Index
> Fetch the complete documentation index at: https://docs.prism.byescaleira.com/llms.txt
> Use this file to discover all available pages before exploring further.

# UserDefaults & Disk

> PrismDefaultsStore for preferences and PrismDiskStore for file-based persistence with TTL and quotas

## PrismDefaultsStore

Type-safe UserDefaults wrapper with Codable support, key prefixing, and observation.

```swift theme={null}
let store = PrismDefaultsStore(suite: "group.myapp", prefix: "app.")

// Codable round-trip
try store.save(settings, forKey: "settings")
let settings = try store.load(AppSettings.self, forKey: "settings")

// Type-safe keys
let themeKey = PrismDefaultKey(name: "theme", defaultValue: "system")
store.set(themeKey, value: "dark")
let theme = store.get(themeKey) // "dark"
```

### Observation

```swift theme={null}
let stream = store.observe(String.self, forKey: "theme")
for await value in stream {
    print("Theme changed: \(value)")
}
```

### SwiftUI Property Wrapper

```swift theme={null}
struct SettingsView: View {
    @PrismDefault(key: "username", defaultValue: "Guest")
    var username: String

    var body: some View {
        TextField("Name", text: $username) // Two-way binding
    }
}
```

## PrismDiskStore

Actor-based file storage with atomic writes, TTL expiration, and disk quota enforcement.

```swift theme={null}
let disk = PrismDiskStore(
    directory: .applicationSupport,
    subdirectory: "MyCache",
    maxSize: 50_000_000, // 50 MB quota
    defaultTTL: 3600     // 1 hour
)

// Basic CRUD
try await disk.save(largePayload, forKey: "report-2024")
let report = try await disk.load(Report.self, forKey: "report-2024")

// TTL per item
try await disk.save(token, forKey: "auth", ttl: 300) // 5 min

// Maintenance
try await disk.pruneExpired()
let bytes = try await disk.totalSize()
```

### Directory Options

| Case                  | Path                 |
| --------------------- | -------------------- |
| `.documents`          | User documents       |
| `.caches`             | System-managed cache |
| `.applicationSupport` | Persistent app data  |
| `.temporary`          | Temp directory       |
| `.custom(URL)`        | Any path             |

### Quota Enforcement

Exceeding `maxSize` throws `PrismStorageError.quotaExceeded(bytes)` on save. Check usage with `totalSize()`.