Error when using interface in grails domain class

Question

I am trying to impelement an interface base domain class with grails and I am runing into error at run time. The error type is Could not determine type for: com.testApp.MyInterface , at table: C .

// in /src/groovy directory
interface    MyInterface{
    int    returnSomething()
}

// in domain class directory 
class   A   implements MyInterface{
    int returnSomething(){
    //a first implementation here
  }
}

class B implements MyInterface{
    int returnSomething(){
    //a second implementation here
  }
}

class C {
    ....
    MyInterface type
    ..............
}

I think because I'm not specifying the real implementation of "MyInterface " in domain class C, grails is getting into trouble when injecting beans at startup. But I would like to keep MyInterface as abstract as possible because differents classes will implement it, various ways. Is there a way to overcome this error? Can I build my models without domain classes extension (I want to avoid that as far as it is possible)?

Answer 1

You need domain classes only if you want to persist data. Without knowing the specifics of your situation, you may want to make classes A, B, and C services rather than domain classes. It has been my experience that sub-classes and interfaces work better in the service realm than the domain class realm. I would imagine that each returnSomething() implementation would operate over distinct domain classes that do not require interfaces.