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import statemachine
import librarybookstate
class Book:
def __init__(self):
self._state = librarybookstate.New()
@property
def state(self):
return self._state
# get behavior/properties from current state
def __getattr__(self, attrname):
attr = getattr(self._state, attrname)
if isinstance(getattr(librarybookstate, attrname, None),
librarybookstate.BookStateTransition):
return lambda: setattr(self, '_state', attr())
return attr
def __str__(self):
return "{0}: {1}".format(self.__class__.__name__, self._state)
class RestrictedBook(Book):
def __init__(self):
super(RestrictedBook, self).__init__()
self._authorized_users = []
def authorize(self, name):
self._authorized_users.append(name)
# specialized checkout to check permission of user first
def checkout(self, user=None):
if user in self._authorized_users:
self._state = self._state.checkout()
else:
raise Exception("{0} could not check out restricted book".format((user, "anonymous")[user is None]))
def run_demo():
book = Book()
book.shelve()
print(book)
book.checkout()
print(book)
book.checkin()
print(book)
book.reserve()
print(book)
try:
book.checkout()
except statemachine.InvalidTransitionException:
print('..cannot check out reserved book')
book.release()
print(book)
book.checkout()
print(book)
print()
restricted_book = RestrictedBook()
restricted_book.authorize("BOB")
restricted_book.restrict()
print(restricted_book)
for name in [None, "BILL", "BOB"]:
try:
restricted_book.checkout(name)
except Exception as e:
print('..' + str(e))
else:
print('checkout to', name)
print(restricted_book)
restricted_book.checkin()
print(restricted_book)
if __name__ == '__main__':
run_demo()
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