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HttpContext

class final

Http context stores arbitrary user defined values and ensures type safety without actually knowing the types. It is backed by a Map and guarantees that keys do not clash.

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class HttpContext {
  set<T>(token: HttpContextToken<T>, value: T): HttpContext
  get<T>(token: HttpContextToken<T>): T
  delete(token: HttpContextToken<unknown>): HttpContext
  keys(): IterableIterator<HttpContextToken<unknown>>
}

Description

This context is mutable and is shared between cloned requests unless explicitly specified.

Further information is available in the Usage Notes...

Methods

Store a value in the context. If a value is already present it will be overwritten.

set<T>(token: HttpContextToken<T>, value: T): HttpContext

Parameters
token HttpContextToken

The reference to an instance of HttpContextToken.

value T

The value to store.

Returns

HttpContext: A reference to itself for easy chaining.

Retrieve the value associated with the given token.

get<T>(token: HttpContextToken<T>): T

Parameters
token HttpContextToken

The reference to an instance of HttpContextToken.

Returns

T: The stored value or default if one is defined.

Delete the value associated with the given token.

delete(token: HttpContextToken<unknown>): HttpContext

Parameters
token HttpContextToken

The reference to an instance of HttpContextToken.

Returns

HttpContext: A reference to itself for easy chaining.

keys(): IterableIterator<HttpContextToken<unknown>>

Parameters

There are no parameters.

Returns

IterableIterator<HttpContextToken<unknown>>: a list of tokens currently stored in the context.

Usage notes

Usage Example

// inside cache.interceptors.ts
export const IS_CACHE_ENABLED = new HttpContextToken<boolean>(() => false);

export class CacheInterceptor implements HttpInterceptor {

  intercept(req: HttpRequest<any>, delegate: HttpHandler): Observable<HttpEvent<any>> {
    if (req.context.get(IS_CACHE_ENABLED) === true) {
      return ...;
    }
    return delegate.handle(req);
  }
}

// inside a service

this.httpClient.get('/api/weather', {
  context: new HttpContext().set(IS_CACHE_ENABLED, true)
}).subscribe(...);

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Licensed under the Creative Commons Attribution License 4.0.
https://angular.io/api/common/http/HttpContext