---
lang: en
title: 'API docs: core.application.lifecycleobserver'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/loopbackio/loopback-next/tree/master/packages/core
permalink: /doc/en/lb4/apidocs.core.application.lifecycleobserver.html
---

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[Home](./index.md) &gt; [@loopback/core](./core.md) &gt; [Application](./core.application.md) &gt; [lifeCycleObserver](./core.application.lifecycleobserver.md)

## Application.lifeCycleObserver() method

Register a life cycle observer class

**Signature:**

```typescript
lifeCycleObserver<T extends LifeCycleObserver>(ctor: Constructor<T>, nameOrOptions?: string | BindingFromClassOptions): Binding<T>;
```

## Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  ctor | [Constructor](./context.constructor.md)<!-- -->&lt;T&gt; | A class implements LifeCycleObserver |
|  nameOrOptions | string \| [BindingFromClassOptions](./context.bindingfromclassoptions.md) | _(Optional)_ Optional name or options for the life cycle observer |

**Returns:**

[Binding](./context.binding.md)<!-- -->&lt;T&gt;