Question about model Injection when recursion is involved.

What is the best way to inject a Model dependency in another Model
where the first Model is injected with the second Model. We did this
accidentally, though may need to do later, and basically crashed the
system. Hopefull won't have to do this but would be nice to know.

I did try getModel() but believe I did something wrong there.

Example

Model A
Model B

Model A
         Inject Model B
         Call Method in B

Model B
        Inject Model A
       Call Method A

Thanks