Step-by-Step Tutorial: Building a NextJS + FastAPI Application

Building a NextJS + FastAPI application can be a great way to create a powerful web application with a powerful frontend and backend framework. In this tutorial, we will go through the steps of building a NextJS application for the frontend and integrating it with a FastAPI backend.

Step 1: Setting up the FastAPI backend

1. Install FastAPI and Uvicorn: First, we need to install FastAPI and Uvicorn, which is a lightning-fast ASGI server.

pip install fastapi uvicorn

1. Create a new directory for your FastAPI project and navigate to it:

mkdir fastapi-backend
cd fastapi-backend

1. Create a new Python file for your FastAPI app, for example, main.py, and import the necessary modules:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def read_root():
    return {"Hello": "World"}

1. Start the FastAPI server using Uvicorn:

uvicorn main:app --reload

Now, you should see the FastAPI server running at http://127.0.0.1:8000.

Step 2: Setting up the NextJS frontend

1. Create a new directory for your NextJS project and navigate to it:

npx create-next-app nextjs-frontend
cd nextjs-frontend

1. Create a new page in the pages directory, for example, index.js, and add some content:

export default function Home() {
  return <h1>Hello, NextJS + FastAPI!</h1>;
}

1. Start the NextJS development server:

npm run dev

Now, you should see your NextJS app running at http://localhost:3000.

Step 3: Integrating the NextJS frontend with the FastAPI backend

1. Create an API route in your FastAPI backend to serve data to your NextJS frontend. Modify your main.py file to include an API route:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def read_root():
    return {"Hello": "World"}

@app.get("/api/data")
async def get_data():
    return {"data": "This is some data from the backend!"}

1. Update your NextJS frontend to fetch data from the API route. Modify your index.js file to include an API call using fetch:

export default function Home({ data }) {
  return <h1>{data}</h1>;
}

export async function getStaticProps() {
  const res = await fetch('http://localhost:8000/api/data');
  const { data } = await res.json();

  return { props: { data } };
}

1. Restart both the FastAPI and NextJS servers, and you should see your NextJS app displaying data fetched from the FastAPI backend.

Congratulations! You have successfully built a NextJS + FastAPI application. This tutorial covers the basics of setting up the frontend and backend, integrating them, and fetching data from the backend in your frontend. Feel free to explore and expand on this foundation to build more complex and feature-rich applications.