pycomposite 1.0.2

Generic implementation of the Composite Design Pattern as a Python class decorator.

Composite Class Decorator

This project contains a generic implementation of the Composite Design Pattern as a Python class decorator.

This is a targeted solution addressing the particular need of creating composite Builders. All existing solutions we observed so far assumed manual reproduction on every abstract method in Composite, which is problematic from a maintenance point of view.

For more technical in-depth discussion please refer to our article: Generic Composite in Python

Usage Example

from abc import ABC, abstractmethod
from typing import Tuple, Any
from pycomposite import composite

class Configuration:
    '''
    Just an example to demostrate side-effect
    '''
    def __init__(self):
        self._configuration = {}
        
    def configure(self, name: str, value: Any) -> None:
        self._configuration[name] = value
        
class Builder(ABC):

    @abstractmethod
    def build_part_one(self, arg: int) -> Tuple: #better coveres a general case
        pass
        
    @abstractmethod
    def build_part_two(self, arg: str) -> Tuple:
        pass
        
    @abstractmethod
    def configure_part_three(self, arg: Configuration) -> None:
        pass

class BuilderA(Builder):

    def build_part_one(self, arg: int) -> Tuple: #better coveres a general case
        return arg*10, arg+5,
        
    def build_part_two(self, arg: str) -> Tuple:
        return f'A: {arg}', 
        
    def configure_part_three(self, arg: Configuration) -> None:
        arg.configure('A', 'A builder')

class BuilderB(Builder):

    def build_part_one(self, arg: int) -> Tuple: #better coveres a general case
        return arg-100, arg*5,
        
    def build_part_two(self, arg: str) -> Tuple:
        return f'B: {arg}', 
        
    def configure_part_three(self, arg: Configuration) -> None:
        arg.configure('B', 'B builder')

@composite
class CompositeBuilder(Builder):
    pass
    
builder = CompositeBuilder(BuilderA(), BuilderB())
config = Configuration()

builder.configure_part_three(config)
assert (70, 12, -93, 35) == builder.build_part_one(7)
assert ('A: high', 'B: high') == builder.build_part_two('high')
assert {'A': 'A builder', 'B': 'B builder'} == config._configuration