80 lines
3.2 KiB
C#
80 lines
3.2 KiB
C#
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#region CPL License
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/*
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Nuclex Framework
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Copyright (C) 2002-2008 Nuclex Development Labs
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This library is free software; you can redistribute it and/or
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modify it under the terms of the IBM Common Public License as
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published by the IBM Corporation; either version 1.0 of the
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License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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IBM Common Public License for more details.
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You should have received a copy of the IBM Common Public
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License along with this library
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*/
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#endregion
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using System;
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using System.Collections.Generic;
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namespace Nuclex.Support.Plugins {
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/// <summary>Employer that directly creates instances of the types in a plugin</summary>
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/// <typeparam name="T">Interface or base class required for the employed types</typeparam>
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/// <remarks>
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/// <para>
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/// This employer directly creates an instance of any type in a plugin assembly that
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/// implements or is derived from the type the generic InstanceEmployer is instanced
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/// to. This is useful when the plugin user already has a special plugin interface
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/// through which additional informations about a plugin type can be queried or
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/// when actually exactly one instance per plugin type is wanted (think of the
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/// prototype pattern for example)
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/// </para>
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/// <para>
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/// Because this employer blindly creates an instance of any compatible type found
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/// in a plugin assembly it should be used with care. If big types with high
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/// construction time or huge memory requirements are loaded this can become
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/// a real resource hog. The intention of this employer was to let the plugin user
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/// define his own factory interface which possibly provides further details about
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/// the type the factory is reponsible for (like a description field). This
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/// factory would then be implemented on the plugin side.
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/// </para>
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/// </remarks>
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public class InstanceEmployer<T> : Employer {
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/// <summary>Initializes a new instance employer</summary>
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public InstanceEmployer() {
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this.employedInstances = new List<T>();
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}
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/// <summary>All instances that have been employed</summary>
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public List<T> Instances {
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get { return this.employedInstances; }
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}
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/// <summary>Determines whether the type suites the employer's requirements</summary>
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/// <param name="type">Type that is checked for employability</param>
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/// <returns>True if the type can be employed</returns>
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public override bool CanEmploy(Type type) {
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return
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Support.HasDefaultConstructor(type) &&
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typeof(T).IsAssignableFrom(type);
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}
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/// <summary>Employs the specified plugin type</summary>
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/// <param name="type">Type to be employed</param>
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public override void Employ(Type type) {
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this.employedInstances.Add((T)Activator.CreateInstance(type));
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}
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/// <summary>All instances employed by the instance employer</summary>
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private List<T> employedInstances;
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}
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} // namespace Nuclex.Support.Plugins
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