# Models - FastAPI Toolsets
Production-ready utilities for FastAPI applications.
Author: d3vyce

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# Models

Added in `v2.0`

Reusable SQLAlchemy 2.0 mixins for common column patterns, designed to be composed freely on any `DeclarativeBase` model.

## Overview

The `models` module provides mixins that each add a single, well-defined column behaviour. They work with standard SQLAlchemy 2.0 declarative syntax and are fully compatible with `AsyncSession`.

    from fastapi_toolsets.models import UUIDMixin, TimestampMixin

    class Article(Base, UUIDMixin, TimestampMixin):
        __tablename__ = "articles"

        title: Mapped[str]
        content: Mapped[str]

All timestamp columns are timezone-aware (`TIMESTAMPTZ`). All defaults are server-side, so they are also applied when inserting rows via raw SQL outside the ORM.

## Mixins

### `UUIDMixin`

Adds a `id: UUID` primary key generated server-side by PostgreSQL using `gen_random_uuid()` (requires PostgreSQL 13+). The value is retrieved via `RETURNING` after insert, so it is available on the Python object immediately after `flush()`.

    from fastapi_toolsets.models import UUIDMixin

    class User(Base, UUIDMixin):
        __tablename__ = "users"

        username: Mapped[str]

    # id is None before flush
    user = User(username="alice")
    await session.flush()
    print(user.id)  # UUID('...')

### `CreatedAtMixin`

Adds a `created_at: datetime` column set to `NOW()` on insert. The column has no `onupdate` hook — it is intentionally immutable after the row is created.

    from fastapi_toolsets.models import UUIDMixin, CreatedAtMixin

    class Order(Base, UUIDMixin, CreatedAtMixin):
        __tablename__ = "orders"

        total: Mapped[float]

### `UpdatedAtMixin`

Adds an `updated_at: datetime` column set to `NOW()` on insert and automatically updated to `NOW()` on every ORM-level update (via SQLAlchemy's `onupdate` hook).

    from fastapi_toolsets.models import UUIDMixin, UpdatedAtMixin

    class Post(Base, UUIDMixin, UpdatedAtMixin):
        __tablename__ = "posts"

        title: Mapped[str]

    post = Post(title="Hello")
    await session.flush()
    await session.refresh(post)

    post.title = "Hello World"
    await session.flush()
    await session.refresh(post)
    print(post.updated_at)

Note

`updated_at` is updated by SQLAlchemy at ORM flush time. If you update rows via raw SQL (e.g. `UPDATE posts SET ...`), the column will not be updated automatically — use a database trigger if you need that guarantee.

### `TimestampMixin`

Convenience mixin that combines `CreatedAtMixin` and `UpdatedAtMixin`. Equivalent to inheriting both.

    from fastapi_toolsets.models import UUIDMixin, TimestampMixin

    class Article(Base, UUIDMixin, TimestampMixin):
        __tablename__ = "articles"

        title: Mapped[str]

## Composing mixins

All mixins can be combined in any order. The only constraint is that exactly one primary key must be defined — either via `UUIDMixin` or directly on the model.

    from fastapi_toolsets.models import UUIDMixin, TimestampMixin

    class Event(Base, UUIDMixin, TimestampMixin):
        __tablename__ = "events"
        name: Mapped[str]

    class Counter(Base, UpdatedAtMixin):
        __tablename__ = "counters"
        id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
        value: Mapped[int]

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