grails - Error occurs when adding inheritance to domain: org.hibernate.TransientObjectException: object references an unsaved transient instance -

i'm having difficulty wrapping head around nature of problem i've been having. have 2 domain classes grails app: headofhousehold , dependent. identical, except in couple of places; firstly, headofhousehold owns dependent using construct: static hasmany = [dependents: dependent], , dependent has static belongsto = [headofhousehold: headofhousehold], secondly dependent has property string type can either spouse or dependent while headofhousehold has transient method gettype() returns self, , lastly there 2 properties currentaddress , previousaddress domain objects contained in headofhousehold, while dependent points headofhousehold's addresses. having trouble doing sort of query use more 1 aspect of current address on dependent decided combine these objects through inheritance query vs parent class of two, , results both headofhousehold , dependent.

so combined them in following way: parent class person

class person {     string firstname     string lastname     string middlename     string suffix     date dateofbirth     date dateadded     string driverslicensenumber     string driverslicensestate     string ssn     string gender     address currentaddress     address previousaddress     mvr mvr     creditreport creditreport     clueauto clueauto     clueproperty clueproperty      static transients =['reportdob','reportdlnumberstate','firstlastmiddlesuffix',                     'reportaddressstring']     static constraints = {             middlename blank: false, nullable: true             suffix blank: true, nullable: true         ssn matches: "[0-9]{9}"         gender blank: true, nullable: true, matches: "m|f"         currentaddress nullable: true         previousaddress blank: true, nullable: true         mvr nullable: true         creditreport nullable: true         clueauto nullable: true         clueproperty nullable: true         dateadded nullable: true     }      public string tostring(){         string returnvalue = lastname + ", " + firstname + " " + middlename         return returnvalue.replaceall("null"," ")     }       //   i'm not sure if correct place these, deal     // transformation necessary create order object send     // off broker in byte[].     def getreportdob(){//dealing dates stupid in java x_x             if(dateofbirth){             gregoriancalendar calendar = new gregoriancalendar()             calendar.settime(dateofbirth)             return datatypefactory.newinstance().newxmlgregoriancalendar(calendar)         }     }      def getreportdlnumberstate(){         return driverslicensenumber +"_" + driverslicensestate     }      def getfirstlastmiddlesuffix(){         return (firstname+"_"+lastname+"_"+middlename+"_"+suffix).replaceall("null","")     }      def getreportaddressstring(){         if(!previousaddress.isempty()){         return "0_home,1_business"         } else{                 return "0_home"             }     }      //todo shouldn't necessary need figure out why is.         def convertgender(){         switch(gender){             case "m":                 return "m"             case "f":                 return "f"             default:                 return null         }         }     } 

child class dependent

class dependent extends person{ string type //relationship head of household.   static belongsto = [headofhousehold: headofhousehold]  static constraints = {  }  public string tostring(){     string returnvalue = lastname + ", " + firstname + " " + middlename     return returnvalue.replaceall("null","") }  def beforeinsert(){     currentaddress = headofhousehold.currentaddress     previousaddress = headofhousehold.previousaddress     dateadded = new date() } 

}

child class headofhousehold

class headofhousehold extends person{    static hasmany = [dependents: dependent] static transients =['type']  static mapping = {  }  static constraints = {   }  def gettype(){     return "self" }   }     

now, works great, except had major problems instantiating objects. kept getting error:

message: error executing bootstraps; nested exception org.hibernate.transientobjectexception: object references unsaved transient instance - save transient instance before flushing: ....clients.address 

which resolved adding addresses directly constructor, , saving addresses afterwards thusly:

address currentaddress = factoryhelperpicardandpike.createcurrentaddress()   address previousaddress = factoryhelperpicardandpike.createpreviousaddress()   headofhousehold hh = factoryhelperpicardandpike.createpicard(picardadded, picardbirthdate, currentaddress, previousaddress)   saveit(currentaddress)   saveit(previousaddress)   saveit(hh) 

instead of:

headofhousehold hh2 = factoryhelperpicardandpike.createpike(pikeadded, picardbirthdate)    address currentaddress2 = factoryhelperpicardandpike.createpikecurrentaddress()    address previousaddress2 = factoryhelperpicardandpike.createpikepreviousaddress()     hh2.setcurrentaddress(currentaddress2)   hh2.setpreviousaddress(previousaddress2)   saveit(currentaddress2)   saveit(previousaddress2)   saveit(hh2) 

i don't understand problem is; , why appeared after added inheritance. able resolve via trial , error, isn't helpful when run problem in future. i've read questions find referring unsaved transient instance, , best can figure error indicates address object considered transient until saved, , reason won't cascade save headofhousehold or dependent. don't understand how different inherited object vs stand alone object. can explain why i'm getting error inherited objects, , not other way? furthermore in depth explanation of error somewhere? i've read this, , isn't illuminating me.

i know long, , appreciate attention.