User:Marcelofinki/Transmogrifier (Computer Science)

Transmogrifier (Computer Science)

(sometimes referred to as Demeter Transmogrifiers)

A Demeter Transmogrifier is a small “wrapper” method used to propagate a method/property implemented in an another subsidiary object.

Sample

Imagine three objects: Driver, Car, Engine.

Object Driver depends on object Car. Object Car depends on object Engine. Object Engine has a method Start.

Driver{
   Car myNewCar = new Car() ;
   myNewCar.Start() ;
}


Car{
   Engine myEngine = new Engine() ;
   public Start(){
      myEngine.Start() ;
   }
}


Engine{
   public Start(){
        // ... some statements ... 
        mySparkPlug.Spark() ;
        // ... some statements ... 
   }
}

In the above example, car.start() is a transmogrifier of engine.start().

Advantage:

Driver does not need to "know" about Engine.

The driver just uses the Start method offered by the Car object. A change on the Engine.Start() method will affect the Car object but not the Driver object, since the driver did not use the myNewCar.myEngine.Start() method.

Disadvantage:

The programmer must code the car.start() method.