In this, our final chapter, we will use the techniques and principles that we have learned up to this point to build a sample web application. This application will use the left-to-right panel design that we explored in Chapter 11, Object-Oriented Programming, which uses the State and Mediator design pattern to control screen state. We will continue to interact with REST endpoints, as we discussed in Chapter 13, Building Applications. We will implement a fully working REST API using Express, that will read data from a backend database. We will then look at some new techniques for working with Observables that will allow us to combine data, filter data, and coordinate asynchronous requests to a REST API. We will also discuss and implement the Domain Events design pattern to help with communication between independent application components.
We already have all of the building blocks and the in-depth knowledge required to put together a sample application at our fingertips, so this chapter is all about reuse and component integration. For the purposes of this chapter, we will extend the Angular sample application that we have been working on, which we last updated in the previous chapter, Chapter 13, Building Applications.
This chapter will cover the following topics:
- Overview of the application
- Database structure
- Building database-driven endpoints with Express
- Design principles of REST API endpoints
- Working with REST API endpoints in Angular
- Using the Observable concatMap function
- Using the Observable forkJoin function
- The Domain Events design pattern
- Raising and consuming Domain Events
- Using the Observable filter function