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context.ts
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/**
* @license
* Copyright Google LLC All Rights Reserved.
*
* Use of this source code is governed by an MIT-style license that can be
* found in the LICENSE file at https://angular.dev/license
*/
/**
* A token used to manipulate and access values stored in `HttpContext`.
*
* @see [Request and response metadata](guide/http/interceptors#request-and-response-metadata)
*
* @publicApi
*/
export class HttpContextToken<T> {
constructor(public readonly defaultValue: () => T) {}
}
/**
* 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.
*
* This context is mutable and is shared between cloned requests unless explicitly specified.
*
* @usageNotes
*
* ### Usage Example
*
* ```ts
* // 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(...);
* ```
*
* @see [Request and response metadata](guide/http/interceptors#request-and-response-metadata)
*
* @publicApi
*/
export class HttpContext {
private readonly map = new Map<HttpContextToken<unknown>, unknown>();
/**
* Store a value in the context. If a value is already present it will be overwritten.
*
* @param token The reference to an instance of `HttpContextToken`.
* @param value The value to store.
*
* @returns A reference to itself for easy chaining.
*/
set<T>(token: HttpContextToken<T>, value: T): HttpContext {
this.map.set(token, value);
return this;
}
/**
* Retrieve the value associated with the given token.
*
* @param token The reference to an instance of `HttpContextToken`.
*
* @returns The stored value or default if one is defined.
*/
get<T>(token: HttpContextToken<T>): T {
if (!this.map.has(token)) {
this.map.set(token, token.defaultValue());
}
return this.map.get(token) as T;
}
/**
* Delete the value associated with the given token.
*
* @param token The reference to an instance of `HttpContextToken`.
*
* @returns A reference to itself for easy chaining.
*/
delete(token: HttpContextToken<unknown>): HttpContext {
this.map.delete(token);
return this;
}
/**
* Checks for existence of a given token.
*
* @param token The reference to an instance of `HttpContextToken`.
*
* @returns True if the token exists, false otherwise.
*/
has(token: HttpContextToken<unknown>): boolean {
return this.map.has(token);
}
/**
* @returns a list of tokens currently stored in the context.
*/
keys(): IterableIterator<HttpContextToken<unknown>> {
return this.map.keys();
}
}