In this chapter, we will be building our ListingApp application. In this section, we will cover the functional requirement list. Our overall application plan can be broken down into three main sections:

• UI layer: The UI aspects involve designing or building the forms, displaying data, routing, and validations.
• Services or middleware layer: We will learn how to write shared services, which will be responsible for backend integrations with APIs and databases.
• Database or fake API setup: We will learn how to set up fake APIs using JSON Server and we will also learn how to create our NoSQL database using Firestore.

Here's the complete list of functional use cases we will be building as part of the learning experience in this chapter:

• Display all the listings
• View listings by ID
• Add a new listing
• Edit a listing
• Delete a listing
• Add comments
• Update comments
• Delete comments
• Edit comments

All the use cases listed will require us to implement HTTP calls. For some, we will need to make POST, GET, and PUT HTTP calls.

Before we proceed any further, now is a good time to bring back all the learning and functionality we have implemented throughout the course of this book. We will need to recollect how we designed and developed our forms, how we captured the form data, how we displayed the data in the component templates, how we implemented routing with parameters, and how we call methods implemented in services inside components. 

We have a lot of work to do, and a load of fun awaits us, so let's get started!