In my recent project, I came across a requirement to create a base class in a managed package with child extension packages would extend to add their value to it.

Before starting the actual work, I thought of googling about experiences of force.com community members about the same. Interestingly I found one relevant link only i.e. this force.com discussion board question. I became doubtful about this working after reading this post, so thought of giving a quick try, before doing it for our customers.

Read More: https://abhinav.fyi/apex-inheritance-extending-managed-package-abstract-virtual-classes-interfaces/