SCALA WORKSHEET: Some ideas around how a Use Case pattern might help.

gistfile1.txt

// REQUESTVAlIDATORS
trait RequestValidator {
  def Validate(): Boolean // various approaches to validating http requests
}

// AUTHPOLICIES
trait AuthPolicy {
  def Authorize() // handle user context and various exceptions
}

// REPO
trait UserRepository {
  def Save(user: User): User
}

// REQUESTS
case class UserRequest(name: String, minimumBalance: Int)

// RESPONSES
case class UserReponse(name: String, minimumBalance: Int)

// DOMAIN
case class User(name: String, age: Int)

// USE CASES
// ### Basic DI that is easy to understand and easy to test.
class CalculateMinimumBalanceUseCase(
  userRepository: UserRepository, // DI
  specialMathLibrary: SpecialMathLibrary
  authPolicy: AuthPolicy,
  userContext: UserContext,
  validators: Seq[RequestValidator]
) {
  def execute(
    userRequest: UserRequest,
    resultHandler: ResultHandler
  ) = {
    // ### Separate auth
    // authPolicy.Authorize()
    // ### Separate request validation
    // validators.all.validator

    // business logic.... do maths.

    // return resultHandler.OnSuccess(minimumBalanace)
    // return resultHandler.OnUnknownUser()
    // return resultHandler.OnUnableToCalculateBalance()
  }

  // ### A response contract that is business readable. Easy to understand. Outlining all behaviour.
  trait ResultHandler {
    def OnSuccess(): Double
    def OnUnkownUser()
  }

}