Service Layer Pattern: Business logic that spans multiple services

Question

In developing an n-tier application, I seem to have hit a scenario where one service say service A needs to consume a method in service B. I do not want to duplicate logic but it does not seem like I should not have services calling one another either. What is the best way to handle this situation without violating any rules? I am thinking about taking the common method out of service B and add to another class and have both services inherit from this class.

Answer 1

Dependency Injection.

Service A expects a well defined service to be injected into it that is expressed with an interface. This way Service B can be injected as well as any other service implementing the same contract.