Support any number of object types for pooling

Question

I am asked to answer the below question as part of a assessment in a hiring process. I have no problem with object return, hence if one could point me in the right direction with class that supports any number of object types I'll be a happy fella.

You are to develop a class that can be used to pool memory by instantiating objects outside of time critical areas and allow consumers to "borrow" and "return" the objects. There should be one implementation of this new class that will support any number of object types for pooling.

Vulpes · Answer

Well I don't think the question is asking you to create a single pool which can contain any type of object as that would make little sense. I think what's needed is a generic class Pool say where T is a reference type as pooling value types again makes little sense. Although there'll only be a single implementation this class will be able to create a separate pool for each T. As there's no point in having more than one pool for any T I'd make the class into a singleton with a static GetInstance method to either create the pool or return the existing instance plus of course a private static field to store the instance and a private instance constructor to create it. The GetInstance method could take a parameter indicating how many objects are to be created initially within the pool As the class will need to instantiate objects of type T you'll also need to add the new() constraint which will restrict T to those classes which have a parameterless constructor. Internally you could use a Queue to store the objects in the pool. When an object is borrowed you can check the Count property to see if there are any existing elements and if there are dequeue one otherwise create a new object and lend that. When an object is returned this can then be enqueued for subsequent reuse.