7. 下面例子分别用观察者模式，事件机制来实现
7.1 实例描述：客户支付了订单款项，这时财务需要开具发票，出纳需要记账，配送员需要配货。
7.2 观察者模式的实现
7.2.1 类图
7.2.2 代码实现
/// <summary>
/// 抽象观察者
/// </summary>
public interface ISubject
{
void Notify();
}
/// <summary>
/// 工作岗位，作为这里的观察者的抽象
/// </summary>
public abstract class JobStation
{
public abstract void Update();
}
/// <summary>
/// 具体主题，这里是客户
/// </summary>
public class Customer : ISubject
{
private string customerState;
private IList<JobStation> observers = new List<JobStation>();
/// <summary>
/// 增加观察者
/// </summary>
/// <param name="observer"></param>
public void Attach(JobStation observer)
{
this.observers.Add(observer);
}
/// <summary>
/// 移除观察者
/// </summary>
/// <param name="observer"></param>
public void Detach(JobStation observer)
{
this.observers.Remove(observer);
}
/// <summary>
/// 客户状态
/// </summary>
public string CustomerState
{
get { return customerState; }
set { customerState = value; }
}
public void Notify()
{
foreach (JobStation o in observers)
{
o.Update();
}
}
}
/// <summary>
/// 会计
/// </summary>
public class Accountant : JobStation
{
private string accountantState;
private Customer customer;
public Accountant(Customer customer)
{
this.customer = customer;
}
/// <summary>
/// 更新状态
/// </summary>
public override void Update()
{
if (customer.CustomerState == "已付款")
{
Console.WriteLine("我是会计，我来开具发票。");
accountantState = "已开发票";
}
}
}
/// <summary>
/// 出纳
/// </summary>
public class Cashier : JobStation
{
private string cashierState;
private Customer customer;
public Cashier(Customer customer)
{
this.customer = customer;
}
public override void Update()
{
if (customer.CustomerState == "已付款")
{
Console.WriteLine("我是出纳员，我给登记入账。");
cashierState = "已入账";
}
}
}
/// <summary>
/// 配送员
/// </summary>
public class Dilliveryman : JobStation
{
private string dillivierymanState;
private Customer customer;
public Dilliveryman(Customer customer)
{
this.customer = customer;
}
public override void Update()
{
if (customer.CustomerState == "已付款")
{
Console.WriteLine("我是配送员，我来发货。");
dillivierymanState = "已发货";
}
}
}
