Learn TypeScript 3 by Building Web Applications

Implementing the loadCountries method

The loadCountries method will be invoked when the controller is initialized (that is, through the constructor).

It will do the following:

1. Ask the population service to retrieve information about the countries.
2. Wait for the API call response.
3. Cache the results.
4. Ask the view to display the countries found.

For the Country cache, we will use Map:

1. Add the following import at the top of the file: import {Country} from "../domain";.
2. Add the following private field on the class: private readonly _countriesMap: Map<string, Country> = new Map<string, Country>();.

Now, implement loadCountries as follows:

async loadCountries(): Promise<void> { console.log("Loading the countries"); try { const countries = await ...