---
name: classable-lifecycle
description: Skill for implementing request/command processing pipelines using Lifecycle. Call this skill when building handler classes with Guards, Pipes, Interceptors, and Filters — following the NestJS-inspired pipeline pattern.
---
# Lifecycle — Request Processing Pipeline
Extend Lifecycle() for pipeline-enabled handlers
`Lifecycle(injects)` extends Injectable with a `static descriptor` field. The descriptor declares the pipeline stages: `guards` (fail-fast), `pipes` (transform input), `interceptors` (wrap execution), `filters` (transform output / catch errors). Each stage is an array of class references.
Implement the correct interface for each stage
- **Guard**: `canActivate(ctx: unknown): boolean | Promise<boolean>` — return false to reject
- **Pipe**: `transform(value: unknown, ctx: unknown): unknown` — transform input args[0]
- **Interceptor**: `intercept(ctx: unknown, next: () => Promise<unknown>): unknown` — wrap the handler
- **Filter**: `transform?(result, ctx)` for success, `catch?(error, ctx)` for errors
Handler must have run() or execute()
The Lifecycle executor looks for `run()` first, then `execute()` on the handler instance. The method receives the (potentially transformed) arguments. Return value passes through filters.
Pipeline execution order
Guards run first (all must pass). Pipes transform `args[0]` sequentially. Interceptors wrap the handler in an onion pattern (last interceptor is innermost). Filters run on the result (or on errors if `.catch()` is defined). Last-filter-wins for errors.
Correct: Full lifecycle pipeline with all stages
./examples/correct-pipeline.ts
Wrong: Common lifecycle mistakes
./examples/wrong-patterns.ts