Unity implements design pattern - observer pattern
The observer design pattern defines a one-to-many combination relationship between objects, so that when the state of an object changes, all objects that depend on it are notified and automatically refreshed.
To put it simply, someone who needs to receive a notification only needs to subscribe to the notification. When the notification is sent, it will be sent to everyone who subscribes to the notification.
Next, use the stock changes to notify people who subscribe to this stock.
1.IInvestor（‘Observer’ interface）
Investor interface
interface IInvestor
{
void Update(Stock stock);
}
2.Investor（‘ConcreteObserver’ class）
Investors concretely realize
class Investor : IInvestor
{
private string _name;
private Stock _stock;
// Constructor
public Investor(string name)
{
this._name = name;
}
public void Update(Stock stock)
{
//Debug.Log("Notified {0} of {1}'s " +"change to {2:C}", _name, stock.Symbol, stock.Price);
Debug.Log("Notified "+ _name+" of "+ stock+"'s " + "change to "+stock.Price);
}
// Gets or sets the stock
public Stock Stock
{
get {
return _stock; }
set {
_stock = value; }
}
}
3.Stock（The ‘Subject’ abstract class）
Stock base class
abstract class Stock
{
private string _symbol;
private double _price;
private List<IInvestor> _investors = new List<IInvestor>();
// Constructor
public Stock(string symbol, double price)
{
this._symbol = symbol;
this._price = price;
}
public void Attach(IInvestor investor)
{
_investors.Add(investor);
}
public void Detach(IInvestor investor)
{
_investors.Remove(investor);
}
public void Notify()
{
foreach (IInvestor investor in _investors)
{
investor.Update(this);
}
Debug.Log("Stock Notify( ) called");
}
// Gets or sets the price
public double Price
{
get {
return _price; }
set
{
if (_price != value)
{
_price = value;
Notify();
}
}
}
// Gets the symbol
public string Symbol
{
get {
return _symbol; }
}
}
4.IBM（‘ConcreteSubject’ class）
'IBM' the stock
class IBM : Stock
{
// Constructor
public IBM(string symbol, double price)
: base(symbol, price)
{
}
}
5. Test
public class ObserverExample1 : MonoBehaviour
{
void Start()
{
// Create IBM stock and attach investors
IBM ibm = new IBM("IBM", 120.00);
ibm.Attach(new Investor("Sorros"));
ibm.Attach(new Investor("Berkshire"));
// Fluctuating prices will notify investors
ibm.Price = 120.10;
ibm.Price = 121.00;
ibm.Price = 120.50;
ibm.Price = 120.75;
}
}