/src/LinFu.IoC/Configuration/Loaders/PostProcessorLoader.cs

 1using System;
 2using System.Collections.Generic;
 3using System.IO;
 4using System.Linq;
 5using LinFu.IoC.Interfaces;
 6using LinFu.Reflection;
 7
 8namespace LinFu.IoC.Configuration.Loaders
 9{
10    /// <summary>
11    ///     A class that automatically loads <see cref="IPostProcessor" />
12    ///     instances and configures a loader to inject those postprocessors
13    ///     into a container upon initialization.
14    /// </summary>
15    internal class PostProcessorLoader : IActionLoader<IServiceContainer, Type>
16    {
17        /// <summary>
18        ///     Determines if the plugin loader can load the <paramref name="inputType" />.
19        /// </summary>
20        /// <remarks>
21        ///     The target type must implement the <see cref="IPostProcessor" /> interface before it can be loaded into
22        ///     memory.
23        /// </remarks>
24        /// <param name="inputType">The target type that might contain the target instance.</param>
25        /// <returns><c>true</c> if the type can be loaded; otherwise, it returns <c>false</c>.</returns>
26        public bool CanLoad(Type inputType)
27        {
28            try
29            {
30                // The type must have a default constructor
31                var defaultConstructor = inputType.GetConstructor(new Type[0]);
32                if (defaultConstructor == null)
33                    return false;
34
35                // It must have the PostProcessorAttribute defined
36                var attributes = inputType.GetCustomAttributes(typeof(PostProcessorAttribute), true);
37                var attributeList = attributes.Cast<PostProcessorAttribute>();
38
39                if (attributeList.Count() == 0)
40                    return false;
41
42                return typeof(IPostProcessor).IsAssignableFrom(inputType);
43            }
44            catch (TypeInitializationException)
45            {
46                // Ignore the error
47                return false;
48            }
49            catch (FileNotFoundException)
50            {
51                // Ignore the error
52                return false;
53            }
54        }
55
56        /// <summary>
57        ///     Loads a set of <see cref="IPostProcessor" /> instances
58        ///     so that they can be loaded into a container upon initialization.
59        /// </summary>
60        /// <param name="inputType">The type that will be used to configure the target loader.</param>
61        /// <returns>A set of <see cref="Action{TTarget}" /> instances. This cannot be <c>null</c>.</returns>
62        public IEnumerable<Action<IServiceContainer>> Load(Type inputType)
63        {
64            var defaultResult = new Action<IServiceContainer>[0];
65
66            // Create the postprocessor instance
67            var instance = Activator.CreateInstance(inputType) as IPostProcessor;
68            if (instance == null)
69                return defaultResult;
70
71            // Inject the postprocessor into any service containers
72            // that will be configured by the current loader instance
73            Action<IServiceContainer> assignPostProcessor =
74                container => container.PostProcessors.Add(instance);
75
76            return new[] {assignPostProcessor};
77        }
78    }
79}