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

Documentation for LoopBack 4

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

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[Home](./index.md) &gt; [@loopback/context](./context.md) &gt; [Context](./context.context.md)

## Context class

Context provides an implementation of Inversion of Control (IoC) container

<b>Signature:</b>

```typescript
export declare class Context extends EventEmitter 
```

## Constructors

|  Constructor | Modifiers | Description |
|  --- | --- | --- |
|  [(constructor)(\_parent, name)](./context.context._constructor_.md) |  | Create a new context. |

## Properties

|  Property | Modifiers | Type | Description |
|  --- | --- | --- | --- |
|  [\_parent](./context.context._parent.md) |  | <code>Context</code> | Parent context |
|  [configResolver](./context.context.configresolver.md) |  | <code>ConfigurationResolver</code> | Configuration resolver |
|  [name](./context.context.name.md) |  | <code>string</code> | Name of the context |
|  [registry](./context.context.registry.md) |  | <code>Map&lt;string, Binding&gt;</code> | Key to binding map as the internal registry |
|  [subscriptionManager](./context.context.subscriptionmanager.md) |  | <code>ContextSubscriptionManager</code> | Manager for observer subscriptions |
|  [tagIndexer](./context.context.tagindexer.md) |  | <code>ContextTagIndexer</code> | Indexer for bindings by tag |

## Methods

|  Method | Modifiers | Description |
|  --- | --- | --- |
|  [\_findByTagIndex(tag)](./context.context._findbytagindex.md) |  | Find bindings by tag leveraging indexes |
|  [\_mergeWithParent(childList, parentList)](./context.context._mergewithparent.md) |  |  |
|  [add(binding)](./context.context.add.md) |  | Add a binding to the context. If a locked binding already exists with the same key, an error will be thrown. |
|  [bind(key)](./context.context.bind.md) |  | Create a binding with the given key in the context. If a locked binding already exists with the same key, an error will be thrown. |
|  [close()](./context.context.close.md) |  | Close the context: clear observers, stop notifications, and remove event listeners from its parent context. |
|  [configure(key)](./context.context.configure.md) |  | Create a corresponding binding for configuration of the target bound by the given key in the context.<!-- -->For example, <code>ctx.configure('controllers.MyController').to({x: 1})</code> will create binding <code>controllers.MyController:$config</code> with value <code>{x: 1}</code>. |
|  [contains(key)](./context.context.contains.md) |  | Check if a binding exists with the given key in the local context without delegating to the parent context |
|  [createView(filter, comparator)](./context.context.createview.md) |  | Create a view of the context chain with the given binding filter |
|  [emitError(err)](./context.context.emiterror.md) |  | Emit an <code>error</code> event |
|  [emitEvent(type, event)](./context.context.emitevent.md) |  | A strongly-typed method to emit context events |
|  [find(pattern)](./context.context.find.md) |  | Find bindings using a key pattern or filter function |
|  [findByTag(tagFilter)](./context.context.findbytag.md) |  | Find bindings using the tag filter. If the filter matches one of the binding tags, the binding is included. |
|  [findOrCreateBinding(key, policy)](./context.context.findorcreatebinding.md) |  | Find or create a binding for the given key |
|  [get(keyWithPath, session)](./context.context.get.md) |  | Get the value bound to the given key, throw an error when no value is bound for the given key. |
|  [get(keyWithPath, options)](./context.context.get_1.md) |  | Get the value bound to the given key, optionally return a (deep) property of the bound value. |
|  [getBinding(key)](./context.context.getbinding.md) |  | Look up a binding by key in the context and its ancestors. If no matching binding is found, an error will be thrown. |
|  [getBinding(key, options)](./context.context.getbinding_1.md) |  | Look up a binding by key in the context and its ancestors. If no matching binding is found and <code>options.optional</code> is not set to true, an error will be thrown. |
|  [getConfig(key, propertyPath, resolutionOptions)](./context.context.getconfig.md) |  | Resolve configuration for the binding by key |
|  [getConfigAsValueOrPromise(key, propertyPath, resolutionOptions)](./context.context.getconfigasvalueorpromise.md) |  | Get the value or promise of configuration for a given binding by key |
|  [getConfigSync(key, propertyPath, resolutionOptions)](./context.context.getconfigsync.md) |  | Resolve configuration synchronously for the binding by key |
|  [getOwnerContext(key)](./context.context.getownercontext.md) |  | Get the owning context for a binding key |
|  [getSync(keyWithPath, session)](./context.context.getsync.md) |  | Get the synchronous value bound to the given key, optionally return a (deep) property of the bound value.<!-- -->This method throws an error if the bound value requires async computation (returns a promise). You should never rely on sync bindings in production code. |
|  [getSync(keyWithPath, options)](./context.context.getsync_1.md) |  | Get the synchronous value bound to the given key, optionally return a (deep) property of the bound value.<!-- -->This method throws an error if the bound value requires async computation (returns a promise). You should never rely on sync bindings in production code. |
|  [inspect(options)](./context.context.inspect.md) |  | Inspect the context and dump out a JSON object representing the context hierarchy |
|  [isBound(key)](./context.context.isbound.md) |  | Check if a key is bound in the context or its ancestors |
|  [isSubscribed(observer)](./context.context.issubscribed.md) |  | Check if an observer is subscribed to this context |
|  [setupConfigurationResolverIfNeeded()](./context.context.setupconfigurationresolverifneeded.md) |  | Set up the configuration resolver if needed |
|  [subscribe(observer)](./context.context.subscribe.md) |  | Add a context event observer to the context |
|  [toJSON()](./context.context.tojson.md) |  | Create a plain JSON object for the context |
|  [unbind(key)](./context.context.unbind.md) |  | Unbind a binding from the context. No parent contexts will be checked. |
|  [unsubscribe(observer)](./context.context.unsubscribe.md) |  | Remove the context event observer from the context |