设计模式之美：Role Object（角色对象）

  1 namespace RoleObjectPattern.Implementation1
  2 {
  3   public abstract class Customer
  4   {
  5     public abstract CustomerRole GetRole(string spec);
  6     public abstract void AddRole(string spec);
  7     public abstract void RemoveRole(string spec);
  8     public abstract bool HasRole(string spec);
  9     public abstract void SomeCommonOperation1();
 10   }
 11 
 12   public class CustomerCore : Customer
 13   {
 14     private Dictionary<string, CustomerRole> _roles
 15       = new Dictionary<string, CustomerRole>();
 16     private CustomerRoleFactory _roleFactory;
 17 
 18     public CustomerCore(CustomerRoleFactory roleFactory)
 19     {
 20       _roleFactory = roleFactory;
 21     }
 22 
 23     public override CustomerRole GetRole(string spec)
 24     {
 25       if (_roles.ContainsKey(spec))
 26         return _roles[spec];
 27       else
 28         return null;
 29     }
 30 
 31     public override void AddRole(string spec)
 32     {
 33       CustomerRole role = GetRole(spec);
 34       if (role == null)
 35       {
 36         role = _roleFactory.CreateRole(spec, this);
 37         if (role != null)
 38         {
 39           _roles.Add(spec, role);
 40         }
 41       }
 42     }
 43 
 44     public override void RemoveRole(string spec)
 45     {
 46       _roles.Remove(spec);
 47     }
 48 
 49     public override bool HasRole(string spec)
 50     {
 51       return _roles.ContainsKey(spec);
 52     }
 53 
 54     public override void SomeCommonOperation1()
 55     {
 56       // do some business logic
 57     }
 58   }
 59 
 60   public class CustomerRole : Customer
 61   {
 62     private CustomerCore _decoratedCore;
 63 
 64     public CustomerRole(CustomerCore core)
 65     {
 66       _decoratedCore = core;
 67     }
 68 
 69     public override CustomerRole GetRole(string spec)
 70     {
 71       return _decoratedCore.GetRole(spec);
 72     }
 73 
 74     public override void AddRole(string spec)
 75     {
 76       _decoratedCore.AddRole(spec);
 77     }
 78 
 79     public override void RemoveRole(string spec)
 80     {
 81       _decoratedCore.RemoveRole(spec);
 82     }
 83 
 84     public override bool HasRole(string spec)
 85     {
 86       return _decoratedCore.HasRole(spec);
 87     }
 88 
 89     public override void SomeCommonOperation1()
 90     {
 91       _decoratedCore.SomeCommonOperation1();
 92     }
 93   }
 94 
 95   public class Borrower : CustomerRole
 96   {
 97     public Borrower(CustomerCore core)
 98       : base(core)
 99     {
100     }
101 
102     public void SomeOperationForBorrower()
103     {
104       // do something for borrower
105     }
106   }
107 
108   public class Investor : CustomerRole
109   {
110     public Investor(CustomerCore core)
111       : base(core)
112     {
113     }
114 
115     public void SomeOperationForInvestor()
116     {
117       // do something for investor
118     }
119   }
120 
121   public class CustomerRoleFactory
122   {
123     public CustomerRole CreateRole(string spec, CustomerCore core)
124     {
125       CustomerRole newRole = null;
126 
127       if (spec == "Borrower")
128       {
129         newRole = new Borrower(core);
130       }
131       else if (spec == "Investor")
132       {
133         newRole = new Investor(core);
134       }
135 
136       return newRole;
137     }
138   }
139 
140   public class Client
141   {
142     public void TestCase1()
143     {
144       Customer customer = new CustomerCore(new CustomerRoleFactory());
145       customer.AddRole("Borrower");
146       customer.AddRole("Investor");
147 
148       CustomerRole customerRole1 = customer.GetRole("Borrower");
149       Borrower borrower = (Borrower)customerRole1;
150       borrower.SomeCommonOperation1();
151       borrower.SomeOperationForBorrower();
152 
153       CustomerRole customerRole2 = customer.GetRole("Investor");
154       Investor investor = (Investor)customerRole2;
155       investor.SomeCommonOperation1();
156       investor.SomeOperationForInvestor();
157     }
158   }
159 }