diapyr

Constructor injection for Python

Overview

Automatic wiring between application objects
Declare what collaborator types you want in your constructor using an @types decorator, they correspond with params
- You can decorate a (factory) function in the same way, in which case the return type must also be declared using 'this' kwarg
- Surround a type in square brackets if you want a list of all matching objects, normally diapyr provides a unique match
Add such classes/factories to a DI instance
- You can also add objects, for example an application config object
Request a type from the DI instance and diapyr will attempt to make it for you, along with the rest of the object graph
Instances are cached in the DI object
- On exit from 'with' clause, dispose is called on any created instances that have it

Manual wiring is messy and tedious especially when an app gets big
Constructor injection avoids spaghetti code
It's trivial to depend on an object anywhere in the graph as long as you don't create a reference cycle e.g. most objects will depend on the same config instance
- No need to resort to globals, which come with a big risk of leaking state between unit tests
Unit testing is easy when an object only interacts with what was passed into its constructor

When depending on a config object the constructor should first extract what it needs and assign those values to fields
Collaborators should also be assigned to fields, and ideally the constructor won't do anything else

Parameter defaults are honoured, this can be used to depend on module log object in real life and pass in a mock in unit tests
Decorating an instance method (without 'this' kwarg) will make it behave as an additional constructor
- Take advantage of name mangling (start with double underscore e.g. __init) to avoid having to call super
Decorating an instance method with 'this' kwarg will make it behave as a factory function
- Adding a class to DI will implicity add all such methods it has as factories
You can play fast and loose with types, diapyr doesn't care whether a factoried object satisfies the declared type

These are generic installation instructions.

The quickest way to get started is to install the current release from PyPI:

pip3 install --user diapyr

If you prefer to keep .local clean, install to a virtualenv:

python3 -m venv venvname
venvname/bin/pip install -U pip
venvname/bin/pip install diapyr
. venvname/bin/activate

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution for diapyr 29
File	Size	Uploaded
diapyr-29.tar.gz	7.5 kB	Jun 22, 2024	Details

Table of built distributions (wheels) for diapyr 29
File	Interpreter	ABI	Platform	Reset
diapyr-29-py2.py3-none-any.whl 10.5 kB Jun 22, 2024	Python 3, Python 2	none	any	Details

Total release size: 18.0 kB

Download URL	diapyr-29.tar.gz
Size	7.5 kB
Tags	Source
SHA-256 checksum How to use checksums	`37132b7e579e93ce5aa7ea9c86d72ea4a374c431a340f4b1a24411601a964763`
BLAKE2b-256 checksum How to use checksums	`d9b23bbec08334764651678e1f3b4daf71b4520f23dabe16621c7e550ab0e53d`
Upload date	Jun 22, 2024
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`twine/3.8.0 pkginfo/1.9.6 readme-renderer/34.0 requests/2.27.1 requests-toolbelt/1.0.0 urllib3/1.26.15 tqdm/4.64.1 importlib-metadata/4.8.3 keyring/23.4.1 rfc3986/1.5.0 colorama/0.4.4 CPython/3.6.9`

Download URL	diapyr-29-py2.py3-none-any.whl
Size	10.5 kB
Tags	Python 2 Python 3
SHA-256 checksum How to use checksums	`db0b38a633b50d5ff58d38f50744e54a12d25358d8e3bd77401cbde8b3185922`
BLAKE2b-256 checksum How to use checksums	`aabab9e76259dfc24250db67550946496cb98be15ec135f6c23a6773a77f1b8a`
Upload date	Jun 22, 2024
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`twine/3.8.0 pkginfo/1.9.6 readme-renderer/34.0 requests/2.27.1 requests-toolbelt/1.0.0 urllib3/1.26.15 tqdm/4.64.1 importlib-metadata/4.8.3 keyring/23.4.1 rfc3986/1.5.0 colorama/0.4.4 CPython/3.6.9`