Extending Angular 2 Observables based service to return data from local Storage.

In previous blog post I have demonstrated using HTML 5 local storage to store data and if not found, service will hit the API end point to fetch data, but I was using the promise approach.

I know these are pretty basic code snippets, but could save me hours if I have documented them – so here I am documenting.

I have manage to do the same thing using the Observerbles ,below is the code snippet for every ones reference.

    getAll(): Observable<IncomeSourceType[]> {
        let types: IncomeSourceType[] = this.storageService.get('IncomeSourceType');

        if (types != null) {
            return Observable.of(types);
        }

        return this.http.get(this.apiUrl)
            .map((response) => {
                let types: IncomeSourceType[] = response.json();
                this.storageService.save('IncomeSourceType', types);
                this.extractData(response);
            })
            .catch(this.handleError);
    }