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Interceptors

PostResolutionInterceptor​

type PostResolutionInterceptor<T> = (ctx: ResolutionContext, instance: T) => T

A function that wraps a resolved instance. Runs after the instance is constructed and @PostConstruct hooks have fired. Must return the (possibly modified or replaced) instance.

Applied per-binding via @Interceptor or .intercept():

// Decorator
@Injectable()
@Interceptor((ctx, instance) => new LoggingProxy(instance))
class PaymentService { ... }

// Fluent API
di.bind(PaymentService)
  .toSelf()
  .intercept((ctx, instance) => new LoggingProxy(instance))

Multiple interceptors on the same binding are chained — each receives the output of the previous one.

PostProcessor​

interface PostProcessor {
  beforeInit(ctx: ResolutionContext, instance: unknown): unknown
  afterInit(ctx: ResolutionContext, instance: unknown): unknown
}

A global hook that runs on every non-bypassed instance in the container. Unlike PostResolutionInterceptor, a PostProcessor is not bound to a specific binding — it sees every instance.

Register a post-processor on the container's postProcessors set before calling init():

class MetricsPostProcessor implements PostProcessor {
  beforeInit(ctx: ResolutionContext, instance: unknown): unknown {
    return instance
  }

  afterInit(ctx: ResolutionContext, instance: unknown): unknown {
    if (instance instanceof Observable) {
      instance.trackMetrics()
    }
    return instance
  }
}

const di = new DiCaf(appModule)
di.postProcessors.add(new MetricsPostProcessor())
await di.init()

Both beforeInit and afterInit must return the instance (or a replacement). Bindings decorated with @BypassPostProcessors or configured with .byPassPostProcessors() are excluded from all post-processors.