Question

I wonder why passing a Command object two-level down of a parent-child class won’t work.

Like this (Class A is parent of B and B is parent of C):

Class A (Creates the instance of the Command object that is passed down to B)

+-- Class B ( Pass down the object to C) 


+------- Class C ( Callsthe execute() method of the Command object)

Whereas, when the instance of the Command object is created in Class B and the passed down to class C it works fine.

Example:

EDIT:

Example (Hand-written code):

public class A {
   private Command command;
   private B b;
   public A() {
     b = new B();
     command = new Command() {
          public void execute() {
            // Do something
          }
     }
     b.setCommand(command);
   }

public class B {
   private Command command;
   private C c;

   public B() {
     c = new C();
     c.setCommand(this.command);
   }

   public void setCommand(Command command){
       this.command = command; 
   }  

}


public class C {
   private Command command;
   public C() {

   }

   public void doStuff() {
       command.execute();
   }
   public void setCommand(Command command){
       this.command = command; 
   }        
}

Answer 1

Problem was that during the process of passing down, the Command object from Class A is assigned to local Command object of Class B, which is the local Command object of Class B is sent to Class C.