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Synopsis

Docker
Python
Flask
SQLAlchemy
Google oAuth 2.0
Marshmallow
Flask-Dance
pip-env
git

Screens

Values

Clean, Readable Code and Design.
Simplicity over Complexity.
Automation.
UI/UX matter.
Build to scale.

Design and Architecture

This application is organized around a MVC pattern.

.
├── config
└── app
    ├── models      # Model
    ├── routes      # Controller
    ├── templates   # View
    ├── forms
    └── static

Modules and features are isolated and decoupled for single responsibility and seperation of concerns.

Organized into Package modules to promote code readability, re-use and collaboration.

.
├── Dockerfile                # Dockerfile is optimized for pip-install Container caching.
├── config                      
│   └── settings.py           # Considered YAML, environment classes inherit from Default class.
├── docker-compose.yml
├── app
│   ├── egu-nyc-dev-001.db    # Required db objects are seeded with Faker.
│   ├── forms
│   │   └── item.py           # Create/Update re-leverage/share unified form.
│   ├── models
│   │   ├── category.py       # Hybrid property/expression to dynamically calc child relationships.
│   │   ├── item.py
│   │   └── user.py
│   ├── routes
│   │   ├── category.py
│   │   ├── errorhandlers.py
│   │   ├── item.py
│   │   ├── main.py           # Leveraged marshmallow for serialization. Single endpoint with nested children.
│   │   └── userauth.py       # Flashes a signal/instance of blueprint and token via Flask-Dance.
│   ├── services
│   ├── static
│   │   ├── img
│   │   │   └── google.png
│   │   └── styles
│   │       └── main.css
│   └── templates             # Limited and avoided logic in templates. Responsive bootstrap with modal window.
│       ├── errors
│       │   ├── 403.html      # Custom error handlers
│       │   ├── 404.html
│       │   └── 500.html
│       ├── item.html
│       ├── layout.html
│       └── main.html
├── manage.py
└── requirements.txt

Hybrid Property vs sqlalchemy_utils @Aggregated

SQLAlchemy-Utils is a popular open source lib that allows for aggregated attributes using @aggregated decorator.

(https://sqlalchemy-utils.readthedocs.io/en/latest/aggregates.html)

The weakness is:

@aggregated decorator requires maintaining an explicit column.
when child is updated, the aggregation trigger does not fire.

Solution:

@hybrid_property and hybrid_expression to develop this phantom/virtual property that crosses functionality between class and instance.

from sqlalchemy_utils import aggregated


class Thread(Base):
    __tablename__ = 'thread'
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.Unicode(255))

    @aggregated('comments', sa.Column(sa.Integer))
    def comment_count(self):
        return sa.func.count('1')

    comments = sa.orm.relationship(
        'Comment',
        backref='thread'
    )

(https://docs.sqlalchemy.org/en/latest/orm/extensions/hybrid.html)

    @hybrid_property
    def item_count(self):
        return len(self.items)

    @item_count.expression
    def item_count(cls):
        return (select([func.count(Item.id)])
                .where(Item.category_id == cls.id)
                .label("item_count"))

API

{URI}/api/v1/catalog/json

Installation

Requirements

Docker (https://www.docker.com/get-started)

Deploy

# Clone this repository using git
cd src/web
docker-compose up --build
# Navigate to http://localhost:8000/

Destroy

docker-compose down -v

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ericcgu/Udacity-Flask-Item-Catalog