python-patterns/specification.py at master · chinmayb/python-patterns · GitHub

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
@author: Gordeev Andrey <gordeev.and.and@gmail.com>

Specification provide recombination business logic by
chaining together using boolean logic
"""

fromabcimportabstractmethod


classSpecification(object):

defand_specification(self, candidate):
raiseNotImplementedError()

defor_specification(self, candidate):
raiseNotImplementedError()

defnot_specification(self):
raiseNotImplementedError()

@abstractmethod
defis_satisfied_by(self, candidate):
pass


classCompositeSpecification(Specification):
@abstractmethod
defis_satisfied_by(self, candidate):
pass

defand_specification(self, candidate):
returnAndSpecification(self, candidate)

defor_specification(self, candidate):
returnOrSpecification(self, candidate)

defnot_specification(self):
returnNotSpecification(self)


classAndSpecification(CompositeSpecification):
_one=Specification()
_other=Specification()

def__init__(self, one, other):
self._one=one
self._other=other

defis_satisfied_by(self, candidate):
returnbool(self._one.is_satisfied_by(candidate) and
self._other.is_satisfied_by(candidate))


classOrSpecification(CompositeSpecification):
_one=Specification()
_other=Specification()

def__init__(self, one, other):
self._one=one
self._other=other

defis_satisfied_by(self, candidate):
returnbool(self._one.is_satisfied_by(candidate) or
self._other.is_satisfied_by(candidate))


classNotSpecification(CompositeSpecification):
_wrapped=Specification()

def__init__(self, wrapped):
self._wrapped=wrapped

defis_satisfied_by(self, candidate):
returnbool(notself._wrapped.is_satisfied_by(candidate))


classUser(object):

def__init__(self, super_user=False):
self.super_user=super_user


classUserSpecification(CompositeSpecification):

defis_satisfied_by(self, candidate):
returnisinstance(candidate, User)


classSuperUserSpecification(CompositeSpecification):

defis_satisfied_by(self, candidate):
returngetattr(candidate, 'super_user', False)


if__name__=='__main__':
print('Specification')
andrey=User()
ivan=User(super_user=True)
vasiliy='not User instance'

root_specification=UserSpecification().\
and_specification(SuperUserSpecification())

print(root_specification.is_satisfied_by(andrey))
print(root_specification.is_satisfied_by(ivan))
print(root_specification.is_satisfied_by(vasiliy))


### OUTPUT ###
# Specification
# False
# True
# False