The problem is as follows: design a basic set of objects/methods to be
used to simulate an elevator bank. What are the objects and their
attributes/methods?
First there is an elevator class. It has a direction (up, down, stand,
maintenance), a current floor and a list of floor requests sorted in the
direction. It receives request from this elevator.
Then there is a bank. It contains the elevators and receives the requests
from the floors. These are scheduled to all active elevators (not in
maintenance).
The scheduling will be like:
- if available pick a standing elevator for this floor.
- else pick an elevator moving to this floor.
- else pick a standing elevator on an other floor.
- else pick the elevator with the lowest load.
Each elevator has a set of states.
- Maintenance: the elevator does not react to external signals (only to its
own signals).
- Stand: the elevator is fixed on a floor. If it receives a call. And the
elevator is on that floor, the doors open. If it is on another floor, it moves
in that direction.
- Up: the elevator moves up. Each time it reaches a floor, it checks if it
needs to stop. If so it stops and opens the doors. It waits for a certain
amount of time and closes the door (unless someting is moving through them.
Then it removes the floor from the request list and checks if there is another
request. If so the elevator starts moving again. If not it enters the state
stand.
- Down: like up but in reverse direction.
There are additional signals:
- alarm. The elevator stops. And if it is on a floor, the doors open, the
request list is cleared, the requests moved back to the bank.
- door open. Opens the doors if an elevator is on a floor and not
moving.
- door closes. Closed the door if they are open.
EDIT: Some elevators don‘t start at bottom/first_floor esp. in case of sky
scrappers. min_floor & max_floor are two additional attributes for
Elevator.
OODesign： Modelling an elevator using Object-Oriented Analysis
and Design
原文：http://www.cnblogs.com/longhorn/p/3536682.html
