why monads

//why monads tutorial

class CompanyInfo { /* important shit here */ }

def getCompanyInfoFromDB(user: User, companyname: String) = ??? //prototype method

//java style classes
class Company { var name: String }
class User { var company: Company }
class Session { var user: User }

def getCompanyInfo(session: Session, newname: String): CompanyInfo {
   //BIG FAT RACE CONDITION, POSSIBLE NPE. NOT THREAD SAFE
   if (session.user != null && session.user.company != null)
     return getCompanyInfoFromDB(session.user, session.user.company.name)
   else
    return null
}

//Functional (mutable) style
class Company { var name: Option[String] }
class User { var company: Option[Company] }
class Session { var user: Option[User] }

def getCompanyInfoDesugared(session: Session, newname: String): Option[CompanyInfo] {
   //what is really happening:
   return session.user.flatMap(user =>
    user.company.flatMap(company =>
                company.name.map(compname =>
            getCompanyInfoFromDB(user, compname)
        )
       )
   )
}
//Equivalent to above code, just using scala's monad syntax
def getCompanyInfoMonadic(session: Session, newname: String): Option[CompanyInfo] {
   //MONADIC STYLE BECAUSE OPTION IS A MONAD!!!
   return for {
    user <- session.user
      company<- user.company //if any of these are None, we terminate and return None
         name<- company.name
        //we could keep going deeper, doesn't matter no nesting syntax!
    } yield
        getCompanyInfoFromDB(user, name)
}