# Django Styleguide

Django styleguide used in [HackSoft](https://hacksoft.io) projects.

Expect often updates as we discuss & decide upon different things.

## Overview

**In Django, business logic should live in:**

* Model properties (with some exceptions).
* Model `clean` method for additional validations (with some exceptions).
* Services - functions, that take care of code written to the database.
* Selectors - functions, that take care of code taken from the database.

**In Django, business logic should not live in:**

* APIs and Views.
* Serializers and Forms.
* Form tags.
* Model `save` method.

**Model properties vs selectors:**

* If the model property spans multiple relations, it should better be a selector.
* If a model property, added to some list API, will cause `N + 1` problem that cannot be easily solved with `select_related`, it should better be a selector.

## Services

A service is a simple function that:

* Live in `your_app/services.py` module
* Takes keyword-only arguments
* Is type-annotated (even if you are not using `mypy` at the moment)
* Does business logic - from simple model creation to complex cross-cutting concerns, to calling external services & tasks.

An example service that creates an user:

```python
def create_user(
    *,
    email: str,
    name: str
) -> User:
    user = User(email=email)
    user.full_clean()
    user.save()

    create_profile(user=user, name=name)
    send_confirmation_email(user=user)

    return user
```

As you can see, this service calls 2 other services - `create_profile` and `send_confirmation_email`