Data services
The two web applications that we have created so far – HealthCheck in Chapters 1 to 3, and WorldCities in Chapters 4 to 7 – both feature front-end to back-end communication over the HTTP(S) protocol, and in order to establish such communication, we made good use of the HttpClient class, a built-in Angular HTTP API client shipped with the @angular/common/http package that rests on the XMLHttpRequest interface.
Angular's HttpClient class has a lot of benefits, including testability features, request and response typed objects, request and response interception, Observable APIs, and streamlined error handling. It can even be used without a data server thanks to the in-memory web API package, which emulates CRUD operations over a RESTful API: we briefly talked about that at the beginning of Chapter 4, Data Model with Entity Framework Core, when we were asking ourselves if we really needed a data server or not (the answer was no, therefore we didn&apos...
