Nuclex.Support/Source/Plugins/InstanceEmployer.cs
Markus Ewald 5f5b8b519b Updated license statement for the year 2010 ;-)
git-svn-id: file:///srv/devel/repo-conversion/nusu@201 d2e56fa2-650e-0410-a79f-9358c0239efd
2010-07-08 12:37:39 +00:00

81 lines
3.3 KiB
C#

#region CPL License
/*
Nuclex Framework
Copyright (C) 2002-2010 Nuclex Development Labs
This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
IBM Common Public License for more details.
You should have received a copy of the IBM Common Public
License along with this library
*/
#endregion
using System;
using System.Collections.Generic;
namespace Nuclex.Support.Plugins {
/// <summary>Employer that directly creates instances of the types in a plugin</summary>
/// <typeparam name="T">Interface or base class required for the employed types</typeparam>
/// <remarks>
/// <para>
/// This employer directly creates an instance of any type in a plugin assembly that
/// implements or is derived from the type the generic InstanceEmployer is instanced
/// to. This is useful when the plugin user already has a special plugin interface
/// through which additional informations about a plugin type can be queried or
/// when actually exactly one instance per plugin type is wanted (think of the
/// prototype pattern for example)
/// </para>
/// <para>
/// Because this employer blindly creates an instance of any compatible type found
/// in a plugin assembly it should be used with care. If big types with high
/// construction time or huge memory requirements are loaded this can become
/// a real resource hog. The intention of this employer was to let the plugin user
/// define his own factory interface which possibly provides further details about
/// the type the factory is reponsible for (like a description field). This
/// factory would then be implemented on the plugin side.
/// </para>
/// </remarks>
public class InstanceEmployer<T> : Employer {
/// <summary>Initializes a new instance employer</summary>
public InstanceEmployer() {
this.employedInstances = new List<T>();
}
/// <summary>All instances that have been employed</summary>
public List<T> Instances {
get { return this.employedInstances; }
}
/// <summary>Determines whether the type suites the employer's requirements</summary>
/// <param name="type">Type that is checked for employability</param>
/// <returns>True if the type can be employed</returns>
public override bool CanEmploy(Type type) {
return
PluginHelper.HasDefaultConstructor(type) &&
typeof(T).IsAssignableFrom(type) &&
!type.ContainsGenericParameters;
}
/// <summary>Employs the specified plugin type</summary>
/// <param name="type">Type to be employed</param>
public override void Employ(Type type) {
this.employedInstances.Add((T)Activator.CreateInstance(type));
}
/// <summary>All instances employed by the instance employer</summary>
private List<T> employedInstances;
}
} // namespace Nuclex.Support.Plugins