We defined a Retrofit service with all API calls, but we haven't connected anything to it yet. It is time to use it. We will extend our code to use Retrofit. Each API call can be executed synchronously or asynchronously. We will show you both ways. Do you remember that we set our Retrofit service base URL to the localhost? This means that we will need a local backend instance that will respond to our HTTP requests. Since backend implementation is not the subject of this book, we will leave it up to you to create a simple service responding to this request. You can implement it from any programming language you like, such as Kotlin, Java, Python, and PHP.
If you are impatient and don't want to implement your own application for dealing with HTTP requests, you can override the base URL, Notes, and TODOs paths as shown in the following example...
