@loopback/docs/site/apidocs/context.contextview.once_1.md

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---
lang: en
title: 'API docs: context.contextview.once_1'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/loopbackio/loopback-next/tree/master/packages/context
permalink: /doc/en/lb4/apidocs.context.contextview.once_1.html
---

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[Home](./index.md) &gt; [@loopback/context](./context.md) &gt; [ContextView](./context.contextview.md) &gt; [once](./context.contextview.once_1.md)

## ContextView.once() method

The "unbind" event is emitted a new binding is removed from the view.

**Signature:**

```typescript
once(eventName: 'unbind', listener: <V>(event: ContextViewEvent<V> & {
        cachedValue?: V;
    }) => void): this;
```

## Parameters

<table><thead><tr><th>

Parameter


</th><th>

Type


</th><th>

Description


</th></tr></thead>
<tbody><tr><td markdown="1">

eventName


</td><td markdown="1">

'unbind'


</td><td markdown="1">

The name of the event - always `unbind`<!-- -->.


</td></tr>
<tr><td markdown="1">

listener


</td><td markdown="1">

&lt;V&gt;(event: [ContextViewEvent](./context.contextviewevent.md)<!-- -->&lt;V&gt; &amp; { cachedValue?: V; }) =&gt; void


</td><td markdown="1">

The listener function to call when the event is emitted.


</td></tr>
</tbody></table>

**Returns:**

this