Question

singleton B initializes singleton A. singleton A has no knowledge of B. How can we use A and be sure that B has done its initialization routine first?

B and A are in different assemblies and are maintained by different teams.

Trying to keep the implementations completely seperate.

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The best answer seems to be just don’t. Here’s what I’m thinking thought:

kick off the initialisation via a registration class that implements a certain interface. If a DoSomething gets called, and T is in an assembly we haven’t seen before, then we search for a class with the given IRegistration interface.

So… that would get rid of the dependency. It’d use reflection. We’d have to look up the types assembly home each time a method got called, but not too high a price to pay perhaps

Answer 1

The level of coupling that your question implies leaves me in serious doubt as to the quality of your design.

1. The answer to your problem is almost certainly not singletons. They should be pretty rare.
2. If A has no knowledge of B, then there should not be any need for A to be initialized after B. Rather, B should be able to use A whether A is initialized first or during B’s initialization.
3. If you have to do this, DON’T use lazy instantiation. Do the initialization in a static constructor and make sure that you reference B before A in any code that needs both.