Question:
In an application using the DDD concepts, I am in doubt about who could inject (dependencies) in a particular class, if there is any standard for this.
It is as follows, between the Application, Domain and Repository layers.
1) A ClienteAppService(Application layer) that needs to inject user, should i inject UsuarioApplicationService and from it call UsuarioService(Domain) or inject UsuarioService directly into ClienteApplicationService?
2) In ClienteService(domain) should I inject UsuarioService and then call UsuarioRepository or could I inject UsuarioRepository directly into ClienteService?
I get worried about cyclic referencing if I keep injecting peer classes.
But I also think that I shouldn't inject another Entity's Repository, because many times the repository's methods have a rule in the service that must be called beforehand.
Has anyone had this question, how do you usually treat it?
Answer:
At the beginning of your text you ask "Who" could inject the dependency into a class.
Dependency injection is the role of the dependency injection infrastructure.
In a dependency graph – "A" depends on "B" – which in turn "B" depends on "C" – which in turn "C" depends on "D" – which in turn "D" depends on "E" – which in turn "E" depends on "F"
All these elements must be injected by the infrastructure. Starting with the creation of F, then E, then D, C, B and finally A.
Circular reference is a problem, avoiding it is necessary.
Boundaries Contexts help limit this dependency on the Boundary Context. You are probably not following this concept regarding DDD.