How do you prevent IDisposable from spreading to all your classes?

Question

Start with these simple classes...

Let\'s say I have a simple set of classes like this:

class Bus
{
    Driver busDriver = new Driver();
}

class          


        

Answer 1

I don't think there is a technical way of preventing IDisposable from spreading if you keep your design so tightly coupled. One should then wonder if the design is right.

In your example, I think it makes sense to have the shoe own the shoelace, and maybe, the driver should own his/her shoes. However, the bus should not own the driver. Typically, bus drivers do not follow buses to the scrapyard :) In the case of drivers and shoes, drivers seldom make their own shoes, meaning they don't really "own" them.

An alternative design could be:

class Bus
{
   IDriver busDriver = null;
   public void SetDriver(IDriver d) { busDriver = d; }
}

class Driver : IDriver
{
   IShoePair shoes = null;
   public void PutShoesOn(IShoePair p) { shoes = p; }
}

class ShoePairWithDisposableLaces : IShoePair, IDisposable
{
   Shoelace lace = new Shoelace();
}

class Shoelace : IDisposable
{
   ...
}

The new design is unfortunately more complicated, as it requires extra classes to instantiate and dispose of concrete instances of shoes and drivers, but this complication is inherent to the problem being solved. The good thing is that buses need no longer be disposable simply for the purpose of disposing of shoelaces.