add-crud-endpoint

name	add-crud-endpoint
description	Step-by-step workflow for adding a new CRUD endpoint to a FastAPI application
license	Apache-2.0

Add a CRUD Endpoint

Follow these steps to add a complete CRUD resource to a FastAPI application.

Step 1: Create the Pydantic Schemas

Create app/schemas/<resource>.py:

from pydantic import BaseModel, ConfigDict

class ItemBase(BaseModel):
    name: str
    description: str | None = None
    price: float

class ItemCreate(ItemBase):
    pass

class ItemUpdate(BaseModel):
    name: str | None = None
    description: str | None = None
    price: float | None = None

class ItemRead(ItemBase):
    id: int
    model_config = ConfigDict(from_attributes=True)

Step 2: Create the ORM Model

Create app/models/<resource>.py:

from sqlalchemy import String, Float, Text
from sqlalchemy.orm import Mapped, mapped_column
from app.db.base import Base

class Item(Base):
    __tablename__ = "items"

    id: Mapped[int] = mapped_column(primary_key=True)
    name: Mapped[str] = mapped_column(String(255))
    description: Mapped[str | None] = mapped_column(Text, default=None)
    price: Mapped[float] = mapped_column(Float)

Step 3: Create the Service Layer

Create app/services/<resource>_service.py:

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession
from app.models.item import Item
from app.schemas.item import ItemCreate, ItemUpdate

async def create_item(db: AsyncSession, payload: ItemCreate) -> Item:
    item = Item(**payload.model_dump())
    db.add(item)
    await db.commit()
    await db.refresh(item)
    return item

async def get_item(db: AsyncSession, item_id: int) -> Item | None:
    return await db.get(Item, item_id)

async def list_items(
    db: AsyncSession, skip: int = 0, limit: int = 100
) -> list[Item]:
    result = await db.execute(select(Item).offset(skip).limit(limit))
    return list(result.scalars().all())

async def update_item(
    db: AsyncSession, item: Item, payload: ItemUpdate
) -> Item:
    for field, value in payload.model_dump(exclude_unset=True).items():
        setattr(item, field, value)
    await db.commit()
    await db.refresh(item)
    return item

  () -> :
     db.delete(item)
     db.commit()

Step 4: Create the Router

Create app/api/v1/endpoints/<resource>.py:

from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession

from app.deps.database import get_db
from app.schemas.item import ItemCreate, ItemRead, ItemUpdate
from app.services import item_service

router = APIRouter()

@router.post("/", response_model=ItemRead, status_code=status.HTTP_201_CREATED)
async def create_item(
    payload: ItemCreate, db: AsyncSession = Depends(get_db)
) -> ItemRead:
    return await item_service.create_item(db, payload)

@router.get("/", response_model=list[ItemRead])
async def list_items(
    skip: int = 0, limit: int = 100, db: AsyncSession = Depends(get_db)
) -> list[ItemRead]:
    return await item_service.list_items(db, skip=skip, limit=limit)

@router.get("/{item_id}", response_model=ItemRead)
async def get_item(
    item_id: int, db: AsyncSession = Depends(get_db)
) -> ItemRead:
    item = await item_service.get_item(db, item_id)
    if  item:
         HTTPException(status_code=, detail=)
     item


  () -> ItemRead:
    item =  item_service.get_item(db, item_id)
      item:
         HTTPException(status_code=, detail=)
      item_service.update_item(db, item, payload)


  () -> :
    item =  item_service.get_item(db, item_id)
      item:
         HTTPException(status_code=, detail=)
     item_service.delete_item(db, item)

Step 5: Register the Router

In app/api/v1/router.py, add:

from app.api.v1.endpoints import items

api_router.include_router(items.router, prefix="/items", tags=["items"])

Step 6: Create a Migration

alembic revision --autogenerate -m "add items table"
alembic upgrade head

Checklist

• Pydantic schemas in app/schemas/
• ORM model in app/models/
• Service functions in app/services/
• Router in app/api/v1/endpoints/
• Router registered in app/api/v1/router.py
• Migration created and applied
• Tests added in tests/