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Implement Strategy Pattern

Table of contents

What is Iterator pattern for?

What is Iterator pattern for?

This pattern changes the behave of the object and like a state pattern but it has little difference.

We want platform that store image but before store the image compress image and apply filter on that. For this goal we use strategy pattern.

compressor_interface.py

Python

import abc
class CompresorInterface(metaclass=abc.ABCMeta):
    @classmethod
    def __subclasshook__(cls, subclass):
        return (
            hasattr(subclass, 'compress') and
            callable(subclass.compress) or
            NotImplemented
        )
    @abc.abstractmethod
    def compress(self, fileName: str):
        raise NotImplementedError

filter_interface.py

Python

import abc
class FilterInterface(metaclass=abc.ABCMeta):
    @classmethod
    def __subclasshook__(cls, subclass):
        return (
            hasattr(subclass, 'apply') and
            callable(subclass.apply) or
            NotImplemented
        )
    @abc.abstractmethod
    def apply(self, fileName: str):
        raise NotImplementedError

Now implement the compressor and filter

black_filter.py

Python

from filter_interface import FilterInterface
class BlackFilter(FilterInterface):
    def apply(self, fileName: str):
        print('Black filter apply on ' + fileName)

jpeg_compressor.py

Python

from compresor_interface import CompresorInterface
class JpegCompress(CompresorInterface):
    def compress(self, fileName: str):
        print('JPEG Compress' + fileName)

In this section we implement storage class

image_storage.py

Python

from compresor_interface import CompresorInterface
from filter_interface import FilterInterface
class ImageStorage:
    def store(
            self,
            fileName: str,
            compressor: CompresorInterface,
            filter: FilterInterface):
        compressor.compress(fileName)
        filter.apply(fileName)

main.py

Python

from image_storage import ImageStorage
from jpeg_compressor import JpegCompress
from black_filter import BlackFilter
def main():
    imageStorag = ImageStorage()
    imageStorag.store(
        'mamad',
        JpegCompress(),
        BlackFilter()
    )
if __name__ == '__main__':
    main()

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