InversionOfControl/Castle.MicroKernel/Registration/Strategies/ServiceDescriptor.cs

   1 // Copyright 2004-2008 Castle Project - http://www.castleproject.org/
   2 //
   3 // Licensed under the Apache License, Version 2.0 (the "License");
   4 // you may not use this file except in compliance with the License.
   5 // You may obtain a copy of the License at
   6 //
   7 //     http://www.apache.org/licenses/LICENSE-2.0
   8 //
   9 // Unless required by applicable law or agreed to in writing, software
  10 // distributed under the License is distributed on an "AS IS" BASIS,
  11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 // See the License for the specific language governing permissions and
  13 // limitations under the License.
  14
  15 namespace Castle.MicroKernel.Registration
  16 {
  17         using System;
  18
  19         /// <summary>
  20         /// Describes how to select a types service.
  21         /// </summary>
  22         public class ServiceDescriptor
  23         {
  24                 public delegate Type ServiceSelector(Type type);
  25
  26                 private readonly TypesDescriptor typesDescriptor;
  27                 private ServiceSelector serviceSelector;
  28
  29                 internal ServiceDescriptor(TypesDescriptor typesDescriptor)
  30                 {
  31                         this.typesDescriptor = typesDescriptor;
  32                 }
  33
  34                 /// <summary>
  35                 /// Uses the base type matched on.
  36                 /// </summary>
  37                 /// <returns></returns>
  38                 public TypesDescriptor Base()
  39                 {
  40                         return Select(delegate { return typesDescriptor.BasedOn; });
  41                 }
  42
  43                 /// <summary>
  44                 /// Uses the first interface of a type.
  45                 /// </summary>
  46                 /// <returns></returns>
  47                 public TypesDescriptor FirstInterface()
  48                 {
  49                         return Select(delegate(Type type)
  50                         {
  51                                 Type first = null;
  52                                 Type[] interfaces = type.GetInterfaces();
  53                                 if (interfaces.Length > 0)
  54                                 {
  55                                         first = interfaces[0];
  56
  57                                         // This is a workaround for a CLR bug in
  58                                         // which GetInterfaces() returns interfaces
  59                                         // with no implementations.
  60                                         if (first.IsGenericType && first.ReflectedType == null)
  61                                         {
  62                                                 first = first.GetGenericTypeDefinition();
  63                                         }
  64                                 }
  65                                 return first;
  66                         });
  67                 }
  68
  69                 /// <summary>
  70                 /// Assigns a custom service selection strategy.
  71                 /// </summary>
  72                 /// <param name="selector"></param>
  73                 /// <returns></returns>
  74                 public TypesDescriptor Select(ServiceSelector selector)
  75                 {
  76                         serviceSelector = selector;
  77                         return typesDescriptor;
  78                 }
  79
  80                 internal Type GetService(Type type)
  81                 {
  82                         if (serviceSelector != null)
  83                         {
  84                                 return serviceSelector(type) ?? type;
  85                         }
  86                         return type;
  87                 }
  88         }
  89 }