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# 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)
        ...

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