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Contribute

This tutorial focuses on the camera service in src/camera.

Install

Make sure you have Python 3 installed (this code is tested with 3.8.5).

Make sure that virtualenv is installed as well. If not, install it with $ sudo apt install python3-virtualenv.

Navigate to src/camera and create a virtual environment that uses Python 3.8:

$ virtualenv --python /usr/bin/python3.8 camera-env

Activate the virtual environment:

$ source camera-env/bin/activate

Install dev packages. Unfortunately pip is a very clumsy package manager that can't handle different environments well. In order to install the dev packages on a non-RasPi computer, you have to make sure, that the RasPi-only dependency picamera is not installed (the installation would fail). Open the file requirements.txt and remove or comment the line picamera ~= 1.13.

Then install all dev dependencies by running:

$ pip install -r requirements-dev.txt

Run tests

Before you run the tests, switch imports of TakePicture in timercam.py and twittercam.py with an imports of MockTakePicture. The files are already prepared, you only need to uncomment and comment the related lines.

Make sure the virtualenv is activated (see above).

Run tests with python -m pytest. It is important to not run pytest directly as this will result in ModuleNotFoundError's.

About Design

We have classes for different purposes.

data classes

data classes are used as data types that store some class of data with the necessary methods to handle it.

data classes should not use other data classes (no aggregation)!

feature classes

feature classes represent a specific feature and hold all data and methods that are related to this feature.

They can make use of data classes (aggregation).

A feature classes create and/or consume data classes.

feature classes should not use other feature classes (no aggregation)!

service classes

service classes represent a service that serves a specifc use case. They are registered with an instance of the runner class which acts as an scheduler.

All service classes have to inherit from abstractService to have the necessary interfaces to interact with the ServiceRunner.

service classes use feature classes to compose their functionality and hold the business logic that brings those features together.