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Use when writing or reviewing Kotlin type declarations to choose @JvmInline value class over data class where appropriate, including Compose stability implications. Technique-layer skill — complements the codebase-specific kotlin-expert.
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Subscription and filter-assembly patterns for the Amethyst relay client layer in `commons/.../relayClient/`. Use when working with compose-scoped subscriptions (`ComposeSubscriptionManager`, `Subscribable`), filter assemblers (`MetadataFilterAssembler`, `ReactionsFilterAssembler`, `FeedMetadataCoordinator`), preloaders (`MetadataPreloader`, `MetadataRateLimiter`), EOSE managers, or any feature that needs to talk to relays lifecycle-aware from a composable. Complements `nostr-expert` (protocol filter syntax) and `kotlin-coroutines` (callbackFlow patterns).
The NIP-85 trusted-assertions model in Quartz (`nip85TrustedAssertions/`) — kind 10040 trust-provider lists, kind 30382 contact cards / user assertions, 30383 event assertions, 30384 addressable assertions, 30385 external-id assertions. Use when building or parsing these events, working with the typed tags (RankTag, HopsTag, FollowerCountTag, ServiceProviderTag/ServiceType, …), wiring a consumer that resolves a 10040 provider entry to the 30382s it signs, ranking on assertion values, or touching the GrapeRank publisher, contact-card nicknames, or the trust projection of an external store.
The NIP-50 indexing surface of Quartz — the `SearchableEvent` interface, which event kinds are searchable, exactly what text each kind's `indexableContent()` contributes, how the SQLite/filesystem stores consume it, and the NIP-50 `SearchQuery` extension grammar plus `SearchRelayListEvent` (kind 10007). Use when making a kind searchable, changing what a kind indexes, diffing the searchable set at a Quartz version bump (external search engines mirror this table), debugging why an event is or isn't found by search, or working with search extensions (`include:spam`, `domain:`, …).
SKILL.md 표시 중
SOC 직업 분류 기준
| name | kotlin-types-value-class |
| description | Use when writing or reviewing Kotlin type declarations to choose @JvmInline value class over data class where appropriate, including Compose stability implications. Technique-layer skill — complements the codebase-specific kotlin-expert. |
Prefer @JvmInline value class for single-field types that carry domain meaning. Data classes are for aggregating multiple fields. A value class gives you type safety (you can't mix up UserId and String) without the allocation overhead of a data class.
String, Long, Int, etc.) used where a domain type would prevent misuse| Situation | Prefer |
|---|---|
Single field + domain-meaningful (UserId, EmailAddress, Percentage) | @JvmInline value class |
| Single field + no domain meaning (just grouping) | Type alias or keep the primitive |
| Multiple fields | Data class |
Needs custom equals/hashCode/toString beyond the wrapped value | Data class (value classes delegate to the underlying type) |
| Used as a generic type argument or nullable in hot paths |
| Data class or primitive (autoboxing cost) |
// GOOD: domain-meaningful single field
@JvmInline value class UserId(val value: String)
@JvmInline value class EmailAddress(val value: String)
@JvmInline value class Percentage(val value: Float)
// BAD: data class wrapping a single field
data class UserId(val value: String) // unnecessary allocation
data class EmailAddress(val value: String) // type safety without the overhead is available
// BAD: value class with no domain meaning
@JvmInline value class Wrapper(val value: String) // just use the String, or a type alias
// BAD: value class needing custom equality
@JvmInline value class CaseInsensitiveString(val value: String)
// value class equals delegates to String equals, which IS case-sensitive
// Use a data class if you need different equality semantics
@JvmInline value class is treated as Stable by the Compose compiler when its underlying type is stable (primitives, String, and other stable types). This means:
@Immutable annotations at Compose boundaries when wrapping primitives or strings// Before: data class wrapping a single field
data class UiState(val userId: String) // works, but allocates a wrapper object
// After: value class is stable and zero-allocation at runtime
@JvmInline value class UserId(val value: String)
data class UiState(val userId: UserId)
UserId?), generic type arguments (List<UserId>), or vararg parameters. In hot paths these allocations matter; in most code they don't.init blocks, lateinit, or delegated properties like by lazy. The class body is extremely constrained — only the single constructor parameter exists.copy(), no component1() for destructuring, and no way to customize toString(). If you need any of these, use a data class.when branches carefully.@Serializable data class A(val value: String) serializes as {"value":"..."}, but a @Serializable value class A(val value: String) serializes as the underlying value ("..."). Replacing a single-field data class with a value class is a breaking change for your API/JSON contract.@Serializable works, but Jackson may need configuration).Any or used in generic contexts, value classes box into a synthetic wrapper class. Java reflection sees mangled method signatures, and frameworks that rely on raw runtime types (some ORMs, DI containers, or serializers) may see the underlying type rather than the value class.A value class can only declare one field, but Compose provides packFloats, packInts, and matching unpack* functions in androidx.compose.ui.util to store multiple primitives in a single Long. This lets you represent composite values (e.g., a 2D point, size, or padding) as a zero-allocation value class instead of a multi-field data class.
@JvmInline value class Offset(val packedValue: Long)
fun Offset(x: Float, y: Float): Offset = Offset(packFloats(x, y))
val Offset.x: Float get() = unpackFloat1(packedValue)
val Offset.y: Float get() = unpackFloat2(packedValue)
androidx.compose.ui.util — packFloats, packInts, unpackFloat1, unpackFloat2, unpackInt1, unpackInt2.| Mistake | Fix |
|---|---|
| Data class wrapping a single domain field | Replace with @JvmInline value class |
| Value class with no domain meaning (just a wrapper) | Use a type alias or the primitive directly |
| Value class needing custom equality | Use a data class instead |
| Value class as generic type argument in hot path | Accept autoboxing cost or use the primitive |
@Immutable annotation on a type that could be a value class | Replace with value class — it's Stable by default |
Forgetting @JvmInline annotation | Always pair value class with @JvmInline for single-field classes |
String, Long, or Int used where different values should not be interchangeable (e.g., fun transfer(from: String, to: String, amount: Long))@Immutable annotation on a single-field wrapperequals/hashCode/toString → data classcompose-stability-diagnostics — diagnose unstable Compose parameters; value classes are one fix