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POHow can I keep track of (enumerate) all classes that implement an interface
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  1. POHow can I keep track of (enumerate) all classes that implement an interface
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    copied!<p>I have a situation where I have an interface that defines how a certain class behaves in order to fill a certain role in my program, but at this point in time I'm not 100% sure how many classes I will write to fill that role. However, at the same time, I know that I want the user to be able to select, from a GUI combo/list box, which concrete class implementing the interface that they want to use to fill a certain role. I want the GUI to be able to enumerate all available classes, but I would prefer not to have to go back and change old code whenever I decide to implement a new class to fill that role (which may be months from now)</p> <p>Some things I've considered: </p> <ol> <li>using an enumeration <ul> <li>Pros: <ol> <li>I know how to do it</li> </ol></li> <li>Cons <ol> <li>I will have to update update the enumeration when I add a new class</li> <li>ugly to iterate through</li> </ol></li> </ul></li> <li>using some kind of <code>static</code> list object in the interface, and adding a new element from within the definition file of the implementing class <ul> <li>Pros: <ol> <li>Wont have to change old code</li> </ol></li> <li>Cons: <ol> <li>Not even sure if this is possible</li> <li>Not sure what kind of information to store so that a factory method can choose the proper constructor ( maybe a map between a string and a function pointer that returns a pointer to an object of the interface )</li> </ol></li> </ul></li> </ol> <p>I'm guessing this is a problem (or similar to a problem) that more experienced programmers have probably come across before (and often), and there is probably a common solution to this kind of problem, which is almost certainly better than anything I'm capable of coming up with. So, how do I do it?</p> <p>(P.S. I searched, but all I found was this, and it's not the same: <a href="https://stackoverflow.com/questions/976208/how-do-i-enumerate-all-items-that-implement-a-generic-interface">How do I enumerate all items that implement a generic interface?</a>. It appears he already knows how to solve the problem I'm trying to figure out.)</p> <p>Edit: I renamed the title to "How can I keep track of... " rather than just "How can I enumerate..." because the original question sounded like I was more interested in examining the runtime environment, where as what I'm really interested in is compile-time book-keeping.</p>
 

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