FastAPI Serializers and Controllers Lab Exercise

Learning Objective: By the end of this lab, you will be able to create and integrate a comments controller in a FastAPI application. This controller will allow users to add, retrieve, update, and delete comments related to teas.

Implementing a Comments Controller in FastAPI

Prerequisites

Before starting, ensure that your application already includes:

• A working CRUD API for teas using FastAPI and SQLAlchemy ORM.
• Pydantic serializers (TeaSchema) to validate and format data.
• The following tea-related API endpoints:

Overview

In this lab, you will:

1. Create a Comments Controller: A new file, controllers/comments.py, to handle comment-related API requests.
2. Implement CRUD Endpoints: Add routes for creating, retrieving, updating, and deleting comments.
3. Test the Endpoints: Use FastAPI’s interactive documentation to ensure all routes work correctly.

Create the Comments Controller

A controller in FastAPI is a module that defines API routes. You will create a new file to handle comment-related operations.

1. Create a new file:
   📂 controllers/comments.py

2. Inside comments.py, set up a router:

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session
from models.comment import CommentModel
from models.tea import TeaModel
from serializers.comment import CommentSchema
from typing import List
from database import get_db

# Initialize the router
router = APIRouter()

Add CRUD Endpoints for Comments

Each endpoint performs a different action on comments. Below is a RESTful API routing table for handling comments.

1️. Get all comments for a tea

This one has been done for you as an example

This endpoint retrieves all comments linked to a specific tea.

@router.get("/teas/{tea_id}/comments", response_model=List[CommentSchema])
def get_comments_for_tea(tea_id: int, db: Session = Depends(get_db)):
    tea = db.query(TeaModel).filter(TeaModel.id == tea_id).first()
    if not tea:
        raise HTTPException(status_code=404, detail="Tea not found")
    return tea.comments

2. Get a single comment by id

This endpoint retrieves a specific comment using its unique ID.

@router.get("/comments/{comment_id}", response_model=CommentSchema)

3. Add a new comment to a tea

This endpoint creates a new comment and links it to an existing tea.

@router.post("/teas/{tea_id}/comments", response_model=CommentSchema)

4. Update an existing comment by id

This endpoint modifies an existing comment.

@router.put("/comments/{comment_id}", response_model=CommentSchema)

5. Delete a comment by id

This endpoint removes a comment from the database.

@router.delete("/comments/{comment_id}")

Register the Comments Controller

For FastAPI to recognize the new routes, you need to register the router in main.py.

Testing Your API

FastAPI provides built-in interactive API documentation to test your endpoints.

1. Run your FastAPI application:

uvicorn main:app --reload

1. Open your browser and go to: http://127.0.0.1:8000/docs

2. Expand the /teas/{tea_id}/comments and /comments/{comment_id} sections.

3. Try creating, retrieving, updating, and deleting comments.