Loading...
My Solution for Design a Vending Machine with Score: 8/10
by alchemy_zephyr540
Requirements
- The Machine needs to present a list of what items is selling and the price
- When a customer come in, he/she can pick an item
- if still have item in stock, he needs to pay: coin, paper cash or card
- if customer pay cash, the machine also needs to give correct change
- if no in stock, display an message
- if still have item in stock, he needs to pay: coin, paper cash or card
- Also need an internal management system:
- to keep track if an inventory like daily, and send out alert if stock is low
- keep the cash storage, if it is full or to low cannot give out change also need to alert the management team
Core Objects & Relationships
VendingMachine:
Inventory
Payments
Transaction
ManagementService
CashStorage
Inventory
Map
addItem(item, count)
checkStock(String id)
removeItem(id)
addItem(id, count)
Payments:
Use Strategy pattern, create a PaymentStrategy Interface:
- CashPaymentStrategy
- CoinPaymentStrategy
- CardPaymentStrategy
Use a factory class to create encapsulate the creation of the correct PaymentStrategy
Also need a Transaction Class to book keeping
- item,
- time
- payment type
- total cash get
- change give out
ManagementService
- check inventory, if the stock is less then MIN_ITEM_COUNT, send out an alert code ITEM_LOW_STOCK
- check cash storage, if cash full send out CASH_FULL alert
- check the coin storage, if coin count less than MIN_COINT_COUNT snedout an LOW_COIN alert
APIs & Class Members (write code)
public class VendingMachine{
private Inventory inventory;
private PaymentProcessor paymentProcessor;
private ManagementService managementService;
private TransactionCollector transaction;
private CashStorage cashStorage;
public boolean vendItem(String itemId, payType, amount);
}
public class Inventory { // singleten
private List<String, Item> items;
private List<String, Integer> stock;
Inventory getInstance();
void addNewItem(Item item, int stock);
boolean refill(String code, int stock);
int getStock(String code)
int sellItem(String item)
}
public class Item{
String code;
String name;
double price;
}
public PaymentProcessor {
PaymentStrategy paymentStrategy;
boolean pay(double amount);
}
public class CashPaymentStrategy implements PaymentProcessor
public class CoinPaymentStrategy implements PaymentProcessor
public class CardPaymentStrategy implements PaymentProcessor
public class PaymentFactory{
PaymentFactory createPaymentStrategy(PaymentType);
}
public enum PaymentType{
CASH,
COIN,
CARD
}
public class TransactionCollector {
List<Transaction> transactions;
addTransaction(Transaction);
getAll();
}
public class Transaction{
Datetime createdAt;
String ItemCode;
String ItemName;
String paymentType;
String amountPaid;
}
public class Alert{
String message;
Type ErroType;
Datetime createdAt;
}
Tradeoffs, SOLID & Scalability
Markdown supported