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POWhat design pattern?
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  1. POWhat design pattern?
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    copied!<p>I have a class A maintaining a list of objects class B. But each object of class B can be referenced in any object of class A. Class B also maintains a list of objects of class A where it is being referenced. The program can and will create (several) objects of both class A and B 'at will' and also delete them.</p> <p>If I use C# I can add and delete objects from both classes with following code</p> <pre><code>public class A { private List&lt;B&gt;ListOfObjects_B; public bool Add(B Object) { bool bAdd = false; if ((Object != null) &amp;&amp; (ListOfObjects_B.IndexOf(B) &lt;0)) { ListOfObjects_B.Add(Object); Object.Add(this); bAdded = true; } return bAdded; } public bool Delete(B Object) { bool bDeleted = ListOfObjects_B.Remove(Object); if (bDeleted == true) Object.Delete(this); return bDeleted; } } public class B { private List&lt;A&gt;ListOfObjects_A; public bool Add(A Object) { bool bAdd = false; if ((Object != null) &amp;&amp; (ListOfObjects_A.IndexOf(A) &lt;0)) { ListOfObjects_A.Add(Object); Object.Add(this); bAdded = true; } return bAdded; } public bool Delete(A Object) { bool bDeleted = ListOfObjects_A.Remove(Object); if (bDeleted == true) Object.Delete(this); return bDeleted; } } </code></pre> <p>This will work as because of removing/adding the object to the ListOfObjects the SECOND time (by recursion) the function will be called it will fail to delete/add thereby avoiding an infinite loop.</p> <p>But I don't like this code even though A and B do not know 'much' about the other class and just call a Delete/Add function.</p> <p>I suppose this kind of problem is general and a design pattern exists for handling it in such a way that recursion can be avoided and updating both lists will be 'just better'. What design pattern should I use? I would appreciate if some code would be added as well. </p>
 

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