Delegable

Summary

Delegable is a simple Python alternative to Ruby on Rails' delegate module, which makes delegation easy. It enables any class to delegate its functions to an instance of another one. Here's an example:

@delegable
class Que:
    def __init__(self):
        self.q = []
        self.delegate('append', 'pop', to='q')

que = Que()
que.append(1)
que.pop()
# => 1

Features:

• Inheritance Safe
• No dependent libraries
• Available for py35, py36, py37, py38

Install

pip install delegable

Getting Started

Basic Usage

Place @delegable.delegator on the top of a class in which you want to enable delegation.

import delegable

@delegable.delegator
class Que:
    def __init__(self, name='default_queue'):
        self._name = name
        self.q = []
        self.delegate('append', 'pop', to='q')

    @property
    def all(self):
        return self.q


que = Que('')
que.append(1)
que.append(2)
que.pop(0)
assert que.all == [2]

Inheritance Safe

It works well with classes inheriting its parent which uses @delegable.delegtor without any problem.

class Que2(Que):
    def __init__(self, name='default_queue'):
        super().__init__(name)

que1 = Que('')
que2 = Que2('')
que1.delegate('append', 'pop', to='q')
que2.delegate('append', 'pop', to='q')
que1.append(1)
que2.append(2)
assert que1.all == [1]
assert que2.all == [2]

delegates

The decorator offers a property, delegates to define delegates all at once. Note it overwrites whole delegates but doesn't merge delegates.

@delegable.delegator
class Que:
    def __init__(self, name='default_queue'):
        self._name = name
        self.q = []
        self.delegate('append', 'pop', to='q')
        self.delegates = {'s': 'join'}

assert que.join('ab') == 'a,b'

que.append(1)
# => AttributeError("'Que' object has no attribute 'append'")

How to Test

This project uses tox to test it against different versions of Python, with underlying pyenv.

Set up

You have to have pyenv installed to run tox in this project.

Test

To test with all versions:

tox

To test with a certain version:

tox -e py37

or

pyenv shell 3.7.7
pytest