Monday, August 19, 2019

Angular CLI - How to cache Http Service calls simply using rxjs

To cache simply in Angular 7 CLI, here used rxjs on HttpClient.

To cache entire country list, we can use as follows,


import { map, catchError, shareReplay } from 'rxjs/operators';
import { throwError, Observable } from 'rxjs';

private countryCache$ = Observable<any>;
  getCountryList() {
    if (!this.countryCache$) {
      this.countryCache$ =
        this.http.get('/api/country/getCountryList')
          .pipe(
            map(response => {
              return response;
            }),
            catchError((error, caught) => {
              return throwError(error);
            }),
            shareReplay(1)
          );

    }
    return this.countryCache$;
  }



To cache object by it's parameter we can use as follows,in this example cached country information by it's name.

private countryInfoCache$ = new Map<string, Observable<any>>();
getCountryInfo(countryName: string) {

    if (!this.countryInfoCache$.get(countryName)) {

      let countryInfoCacheResult =
        this.http.get('/api/country/getCountryInfoByName',
          { 'countryName': countryName })
          .pipe(
            map(response => {
              return response;
            }),
            catchError((error, caught) => {
              return throwError(error);
            }),
            shareReplay(1)
          );

      this.countryInfoCache$.set(countryName, countryInfoCacheResult);
    }
    return this.countryInfoCache$.get(countryName);

  }

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