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POSolving a library design - centralised configuration reference
 

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  1. POSolving a library design - centralised configuration reference
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    <p>Consider the sample code below consisting of a Class Library <em>design</em> and an executable Program using the library.</p> <pre><code>namespace AppLib { /// &lt;summary&gt; /// Entry point for library. Stage manages all the actors in the logic. /// &lt;/summary&gt; class StageApp { /// &lt;summary&gt; /// Setting that is looked up by different actors /// &lt;/summary&gt; public int SharedSetting { get; set; } /// &lt;summary&gt; /// Stage managing actors with app logic /// &lt;/summary&gt; public IEnumerable&lt;Actor&gt; Actors { get { return m_actors.Where(x =&gt; x.Execute() &gt; 40).ToArray(); } } private List&lt;Actor&gt; m_actors = new List&lt;Actor&gt;(); } /// &lt;summary&gt; /// An object on the stage. Refers to stage (shared)settings and execute depending on the settings. /// Hence actor should have reference to stage /// &lt;/summary&gt; class Actor { private StageApp m_StageApp; private int m_Property; /// &lt;summary&gt; /// An actor that needs to refer to stage to know what behavior to execute /// &lt;/summary&gt; /// &lt;param name="stage"&gt;&lt;/param&gt; public Actor(StageApp stage) { m_StageApp = stage; m_Property = new Random().Next(); } /// &lt;summary&gt; /// Execute according to stage settings /// &lt;/summary&gt; /// &lt;returns&gt;&lt;/returns&gt; public int Execute() { return m_StageApp.SharedSetting * m_Property; } } } namespace AppExe { using AppLib; class Program { static void Main(string[] args) { StageApp app = new StageApp(); app.SharedSetting = 5; // Question: How to add actor to stage? foreach (var actor in app.Actors) Console.WriteLine(actor.Execute()); } } } </code></pre> <p><strong>Question</strong></p> <p><code>Stage</code> and <code>Actor</code> have circular dependency and seems bad to me. For example, how should we add actors to stage?</p> <p>If I let user to create new <code>Actor()</code> themselves, then they must keep on supplying the <code>Stage</code>.</p> <p>If I give <code>Actor()</code> an internal constructor and make <code>Stage</code> a factory, then I lose some of the flexibility for users to do making inherited <code>Actor</code>s.</p> <p>If I make <code>Stage</code> a singleton, then I can only have one set of <code>SharedSetting</code>. In case the user wants more than one <code>Stage</code> in his <code>AppExe</code>, then it cannot be done.</p> <p>Is there anyway to redesign the architecture so as to avoid the problems above?</p>
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