1 //
2 // InstanceExtensionNode.cs
3 //
4 // Author:
5 //   Lluis Sanchez Gual
6 //
7 // Copyright (C) 2007 Novell, Inc (http://www.novell.com)
8 //
9 // Permission is hereby granted, free of charge, to any person obtaining
10 // a copy of this software and associated documentation files (the
11 // "Software"), to deal in the Software without restriction, including
12 // without limitation the rights to use, copy, modify, merge, publish,
13 // distribute, sublicense, and/or sell copies of the Software, and to
14 // permit persons to whom the Software is furnished to do so, subject to
15 // the following conditions:
16 //
17 // The above copyright notice and this permission notice shall be
18 // included in all copies or substantial portions of the Software.
19 //
20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
24 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
25 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
26 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
27 //
28 
29 
30 using System;
31 
32 namespace Mono.Addins
33 {
34 	/// <summary>
35 	/// Base class for extension nodes which create extension objects
36 	/// </summary>
37 	public abstract class InstanceExtensionNode: ExtensionNode
38 	{
39 		object cachedInstance;
40 
41 		/// <summary>
42 		/// Gets the extension object declared by this node
43 		/// </summary>
44 		/// <param name="expectedType">
45 		/// Expected object type. An exception will be thrown if the object is not an instance of the specified type.
46 		/// </param>
47 		/// <returns>
48 		/// The extension object
49 		/// </returns>
50 		/// <remarks>
51 		/// The extension object is cached and the same instance will be returned at every call.
52 		/// </remarks>
GetInstance(Type expectedType)53 		public object GetInstance (Type expectedType)
54 		{
55 			object ob = GetInstance ();
56 			if (!expectedType.IsInstanceOfType (ob))
57 				throw new InvalidOperationException (string.Format ("Expected subclass of type '{0}'. Found '{1}'.", expectedType, ob.GetType ()));
58 			return ob;
59 		}
60 
61 		/// <summary>
62 		/// Gets the extension object declared by this node
63 		/// </summary>
64 		/// <returns>
65 		/// The extension object
66 		/// </returns>
67 		/// <remarks>
68 		/// The extension object is cached and the same instance will be returned at every call.
69 		/// </remarks>
GetInstance()70 		public object GetInstance ()
71 		{
72 			if (cachedInstance == null)
73 				cachedInstance = CreateInstance ();
74 			return cachedInstance;
75 		}
76 
77 		/// <summary>
78 		/// Creates a new extension object
79 		/// </summary>
80 		/// <param name="expectedType">
81 		/// Expected object type. An exception will be thrown if the object is not an instance of the specified type.
82 		/// </param>
83 		/// <returns>
84 		/// The extension object
85 		/// </returns>
CreateInstance(Type expectedType)86 		public object CreateInstance (Type expectedType)
87 		{
88 			object ob = CreateInstance ();
89 			if (!expectedType.IsInstanceOfType (ob))
90 				throw new InvalidOperationException (string.Format ("Expected subclass of type '{0}'. Found '{1}'.", expectedType, ob.GetType ()));
91 			return ob;
92 		}
93 
94 		/// <summary>
95 		/// Creates a new extension object
96 		/// </summary>
97 		/// <returns>
98 		/// The extension object
99 		/// </returns>
CreateInstance()100 		public abstract object CreateInstance ();
101 	}
102 }
103