API

An API is the only way to access other third party source for data or to access the database. The API is stored in the api directory of the module or app. The API is a function that returns a promise. Our API Uses the Interface Segregation Pattern. the Api is injected in the service layer via the dependency injection pattern. The API is used in the service layer. An example of an API is given below.

Creating your own api

Let's create an api called fetchAllCounts.ts in the api directory.

import Count from "../model/Count";
import application from "src/resources/configs/application";

export default function fetchAllCounts(): Promise<Count[]> {
  return fetch(`https://${application.backend}/counts``)
    .then((response) => response.json())
    .then((json) => json as Count[]);
}

import Count from "../model/Count";
import application from "src/resources/configs/application";

export default function fetchAllCounts(): Promise<Count[]> {
  return fetch(`https://${application.backend}/counts``)
    .then((response) => response.json())
    .then((json) => json as Count[]);
}

Registering your own api

in the api folder there is a file called index.ts where the api is registered. Let's register the fetchAllCounts api in the index.ts file.

import Count from "../model/Count";
import fetchAllCounts from "./fetchAllCounts";

export interface CountApi {
  fetchAllCounts?: () => Promise<Count[]>;
}

const api: CountApi = {
  fetchAllCounts,
};

export default api;

import Count from "../model/Count";
import fetchAllCounts from "./fetchAllCounts";

export interface CountApi {
  fetchAllCounts?: () => Promise<Count[]>;
}

const api: CountApi = {
  fetchAllCounts,
};

export default api;

Note: Here the fetchAllCounts function is an optional function because when testing we might not want to pass the fetchAllCounts function as a mock instead other one can be done. So, we make the function optional.

Now the api has been registered into your module. to register it to the app and to be able to use it on the service layer you have to register it in the src/api.ts file.

import countApi, { CountApi } from "./app/api";

export interface Api {
  count?: CountApi;
}

const api: Api = {
  count: countApi,
};
export default api;

import countApi, { CountApi } from "./app/api";

export interface Api {
  count?: CountApi;
}

const api: Api = {
  count: countApi,
};
export default api;

now this will be automatically dependency injected into the service layer.