Object serialization/Oz

This example uses internal implementation details and may not work in future Mozart versions.

First a module that defines a base class and functions for marshalling/unmarshalling:

<lang oz>functor import

  Module

export

  Mixin
  InstantiateMarshaller

define

  class Mixin
     meth initUninitialized skip end
    
     meth toData($)

As = {Arity {GetClass self}.{AtomToName 'ooAttr'}} Fs = {Arity {GetClass self}.{AtomToName 'ooFeat'}}

     in

{Map As fun {$ A} A#@A end} #{Map Fs fun {$ F} F#self.F end}

     end
     
     meth fromData(Data) As#Fs = Data in

{ForAll As proc {$ A#V} A := V end} {ForAll Fs proc {$ F#V} self.F = V end}

     end
  end

  fun {InstantiateMarshaller Classes}
     ClassByName = {List.toRecord unit

{List.zip {Map Classes GetClassName} Classes fun {$ N C} N#C end}}

     fun {Unmarshal ClassName#Data}

O = {New ClassByName.ClassName initUninitialized}

     in

{O fromData(Data)} O

     end
  in
     module(marshal:Marshal

unmarshal:Unmarshal )

  end
  
  %% Result: pair of class name and object data
  fun {Marshal Object}
     {GetClassName {GetClass Object}}#{Object toData($)}
  end

  fun {GetClassName Class}
     Class.{AtomToName 'ooPrintName'}
  end
 
  %% Get access to two internal, implementation-dependent functions
  local
     [Boot_Object Boot_Name] = {Module.link ['x-oz://boot/Object' 'x-oz://boot/Name']}
  in
     GetClass = Boot_Object.getClass
     AtomToName = Boot_Name.newUnique
  end

end</lang>

An example application, inspired by the C++ example:

<lang oz>functor import

  Application
  ObjectMarshalling
  Pickle
  System

define

 local
    Count = {NewCell 1}
 in
    class Employee from ObjectMarshalling.mixin

feat name department id

meth init(Department Name) self.name = Name self.department = Department self.id = Count := @Count + 1 end

meth print($) "Id:"#self.id#", name: "#self.name#", dep.: "#self.department end

    end
 end
 
 class Worker from Employee
    feat

salary

    meth init(Department Name Salary)

Employee, init(Department Name) self.salary = Salary

    end
    
    meth print($)

Employee, print($)#", wage per hour: "#self.salary

    end
 end

 Marshaller = {ObjectMarshalling.instantiateMarshaller [Employee Worker]}
 
 Employees = [{New Employee init("maintenance" "Fritz Schmalstieg")}

{New Employee init("repair" "John Berry")} {New Worker init("maintenance" "Laurent Le Chef" 20.0)} {New Worker init("IT" "Srinivan Taraman" 55.35)} ]

 {System.showInfo "Original objects:"}
 for E in Employees do {System.showInfo {E print($)}} end

 {Pickle.save {Map Employees Marshaller.marshal} "objects.dat"}

 EmployeesFromDisk = {Map {Pickle.load "objects.dat"} Marshaller.unmarshal}

 {System.showInfo "Loaded objects:"}
 for E in EmployeesFromDisk do {System.showInfo {E print($)}} end

 {Application.exit 0}

end</lang>