obscache

In-memory cache service for Angular with RxJS.

Example

import { HttpClient } from "@angular/common/http";
import { Injectable } from "@angular/core";
import { CacheService } from "obscache";
import { Observable } from "rxjs";

export interface Article {
  id: string;
  title: string;
  content: string;
}

@Injectable()
export class ArticleService {
  constructor(private http: HttpClient, private cache: CacheService) {}

  get(id: string): Observable<Article> {
    return this.cache.get(`article:${id}`)
      .miss(() => ({
        value: this.http.get(`/api/articles/${id}`),
        expires: "15m"
      }));
  }
}

The get method in the example above returns an observable of article data. If the cache key article:${id} exists in cache, the cached value will be emitted immediately when it's subscribed. Otherwise the callback of the miss function will be invoked, and the returned value will be cached and emitted.

Future changes to the cache will notify previously subscribed observers. Say someone calls the get method again after 15 minutes, by then the cached article data has expired. The miss call will be triggered again and latest article data will be retrieved. It's likely that previously subscribed observers are also interested in the new data, so they will also get notified. If, however, you don't want future changes, just call take(1) or first() before subscribing.

The returned observable is cold. So no miss call will be made if no one subscribes to it.