Dependencies¶
FastAPI dependency factories for automatic model resolution from path and body parameters.
Overview¶
The dependencies module provides two factory functions that create FastAPI dependencies to fetch a model instance from the database automatically — either from a path parameter or from a request body field — and inject it directly into your route handler.
PathDependency¶
PathDependency resolves a model from a URL path parameter and injects it into the route handler. Raises NotFoundError automatically if the record does not exist.
from fastapi_toolsets.dependencies import PathDependency
UserDep = PathDependency(model=User, field=User.id, session_dep=get_db)
@router.get("/users/{user_id}")
async def get_user(user: User = UserDep):
return user
By default the parameter name is inferred from the field (user_id for User.id). You can override it:
UserDep = PathDependency(model=User, field=User.id, session_dep=get_db, param_name="id")
@router.get("/users/{id}")
async def get_user(user: User = UserDep):
return user
BodyDependency¶
BodyDependency resolves a model from a field in the request body. Useful when a body contains a foreign key and you want the full object injected:
from fastapi_toolsets.dependencies import BodyDependency
RoleDep = BodyDependency(model=Role, field=Role.id, session_dep=get_db, body_field="role_id")
@router.post("/users")
async def create_user(body: UserCreateSchema, role: Role = RoleDep):
user = User(username=body.username, role=role)
...