Adding Comments to the Social Media API

In this section, we’ll extend our social media API to allow users to add comments to existing posts. We’ll utilize FastAPI’s powerful data modeling and relationship capabilities to create a robust and efficient commenting system.

Setting Up the Data Model

First, we’ll define a data model for comments:

Python

from pydantic import BaseModel

class Comment(BaseModel):
    content: str
    user_id: int
    post_id: int

This model ensures that comments have a content field, a user_id field, and a post_id field to associate them with specific posts.

Creating a POST Endpoint

Next, we’ll create a POST endpoint to handle the creation of comments:

Python

from fastapi import APIRouter, HTTPException

router = APIRouter()

@router.post("/posts/{post_id}/comments")
async def create_comment(post_id: int, comment: Comment, db: Session = Depends(get_db)):
    post = db.query(Post).filter(Post.id == post_id).first()
    if not post:
        raise HTTPException(status_code=404, detail="Post    not found")

    new_comment = CommentModel(content=comment.content, user_id=comment.user_id, post_id=post_id)
    db.add(new_comment)
    db.commit()
    db.refresh(new_comment)
    return new_comment

Explanation:

• The @router.post("/posts/{post_id}/comments") decorator defines a POST endpoint for creating comments on a specific post.
• The post_id path parameter is used to identify the target post.
• The comment argument is used to receive the comment data.
• The db.query(Post).filter(Post.id == post_id).first() line retrieves the post with the specified ID from the database.
• If the post is not found, a 404 HTTPException is raised.
• A new CommentModel instance is created using the comment data and the post ID.
• The new comment is added to the database session.
• The changes are committed to the database.
• The created comment is refreshed to get its assigned ID.
• The created comment is returned as a response.

Retrieving Comments for a Post

To retrieve comments for a specific post, you can create a GET endpoint:

Python

@router.get("/posts/{post_id}/comments")
async def get_comments(post_id: int, db: Session = Depends(get_db)):
    comments = db.query(Comment).filter(Comment.post_id == post_id).all()
    return comments