Chain Responsibility Design Pattern Example in Python

chain_responsibility_example.py

# Chain Responsibility Design Pattern Example in Python
from abc import abstractmethod


class LeaveRequest:
    def __init__(self, date: int):
        self.date = date

    def get(self) -> int:
        return self.date


class Approver:
    def __init__(self):
        self.next_approver = None

    def set_next(self, approver):
        self.next_approver = approver
        return self.next_approver

    def approved_leave(self, request: LeaveRequest):
        if self.can_approve(request.get()):
            self.do_approving(request)

        else:
            self.next_approver.approved_leave(request)

    @abstractmethod
    def can_approve(self, num_date: int) -> bool:
        pass

    @abstractmethod
    def do_approving(self, request: LeaveRequest):
        pass


class Supervisor(Approver):
    def __int__(self):
        super().__init__()

    @abstractmethod
    def do_approving(self, request: LeaveRequest):
        print("Supervisor approved ", request.get())

    def can_approve(self, num_date: int) -> bool:
        return num_date <= 3


class DeliverManager(Approver):
    def __int__(self):
        super().__init__()

    @abstractmethod
    def do_approving(self, request: LeaveRequest):
        print("Deliver Manager approved ", request.get())

    def can_approve(self, num_date: int) -> bool:
        return 3 < num_date <= 5


class Director(Approver):
    def __int__(self):
        super().__init__()

    @abstractmethod
    def do_approving(self, request: LeaveRequest):
        print("Director approved ", request.get())

    def can_approve(self, num_date: int) -> bool:
        return num_date > 5


def get_approved():
    supervisor = Supervisor()
    deliver = supervisor.set_next(DeliverManager())
    deliver.set_next(Director())
    return supervisor


if __name__ == '__main__':
    approve = get_approved()

    leave_request = LeaveRequest(3)
    approve.approved_leave(leave_request)

    leave_request = LeaveRequest(4)
    approve.approved_leave(leave_request)

    leave_request = LeaveRequest(5)
    approve.approved_leave(leave_request)

    leave_request = LeaveRequest(6)
    approve.approved_leave(leave_request)