AgentSkillsCN

effect-layers-services

定义服务、划分层级、构建依赖关系，并实现线上与测试环境的切换。适用于 DI 边界及应用组合场景。

SKILL.md
--- frontmatter
name: effect-layers-services
description: Define services, provide layers, compose dependencies, and switch live/test. Use for DI boundaries and app composition.
allowed-tools: Read, Grep, Glob, Edit, Write, mcp__effect-docs__effect_docs_search

Layers & Services

When to use

  • •You need DI boundaries or swapping test/live implementations
  • •You want to compose infra (logger, db, http) once for the app

Define Service

ts
class UserRepo extends Effect.Service<UserRepo>()("UserRepo", {
  sync: () => ({ find: (id: string) => Effect.succeed({ id }) })
}) {}

Provide Layer

ts
const program = Effect.gen(function* () {
  const repo = yield* UserRepo
  return yield* repo.find("123")
}).pipe(Effect.provide(UserRepo.Default))

Compose

ts
const AppLayer = Layer.merge(UserRepo.Default, Logger.Default)

Test vs Live

ts
const layer = process.env.NODE_ENV === "test" ? UserRepoTest : UserRepo.Default

Guidance

  • •Services define interfaces; Layers bind implementations
  • •Compose layers at the app boundary; keep handlers unaware of wiring
  • •Use .Default for quick live/test setup; add custom layers as needed

Pitfalls

  • •Circular layer dependencies → split modules, provide from above
  • •Providing layers too deep → centralize to avoid duplication and confusion

Cross-links

Local Source Reference

CRITICAL: Search local Effect source before implementing

The full Effect source code is available at docs/effect-source/. Always search the actual implementation before writing Effect code.

Key Source Files

  • •Layer: docs/effect-source/effect/src/Layer.ts
  • •Effect: docs/effect-source/effect/src/Effect.ts
  • •Context: docs/effect-source/effect/src/Context.ts

Example Searches

bash
# Find Layer composition patterns
grep -F "Layer.merge" docs/effect-source/effect/src/Layer.ts
grep -F "Layer.provide" docs/effect-source/effect/src/Layer.ts

# Study Effect.Service patterns
grep -F "Effect.Service" docs/effect-source/effect/src/Effect.ts

# Find Context usage
grep -F "Tag" docs/effect-source/effect/src/Context.ts
grep -F "make" docs/effect-source/effect/src/Context.ts

# Look at Layer test examples
grep -F "Layer." docs/effect-source/effect/test/Layer.test.ts

Workflow

  1. •Identify the Layer or Service API you need
  2. •Search docs/effect-source/effect/src/Layer.ts for the implementation
  3. •Study the types and composition patterns
  4. •Look at test files for usage examples
  5. •Write your code based on real implementations

Real source code > documentation > assumptions

References