Passing subtypes as Function parameters

To date I've been using an array of Joints() and an array of Objects(). I realized it'd be smarter to consolidate the two, so the Object class now has a joint field...

TYPE joint
   Field pos.vector
   field joint_type
END TYPE

TYPE obj
   Field pos.vector
   Field size
   Field joint.joint
END TYPE

DIM objects.obj(10)

FOR n=0 to 10
   objects(n)=NEW obj
   objects(n)\pos.vector=NEW vector
   objects(n)\joint.joint=NEW joint
   objects(n)\joint\pos.vector=NEW vector
NEXT

Only now my function create_joint doesn't work.

FUNCTION Create_Joint(j.joint)
   IF j\joint_type
      blah blah blah
   END IF
END FUNCTION

The object 'j' = Null ; it hasn't been created when called with Create_Joint(objects(n)\joint)

How do I pass the joint sub-object as a function parameter?

If you attempted to Create_Joint(objects(n)\joint) after the For...Next, n=11 therefor it is Null. You should try calling the function within the For...Next.

Type vector
	Field x#
	Field y#
	Field z#	
End Type

Type joint
   Field pos.vector
   Field joint_type
End Type

Type obj
   Field pos.vector
   Field size
   Field joint.joint
End Type

Dim objects.obj(10)

For n=0 To 10
   objects(n)=New obj
   objects(n)\pos.vector=New vector
   objects(n)\joint.joint=New joint
   objects(n)\joint\joint_type=n ;<-- a lil test
   objects(n)\joint\pos.vector=New vector
   Create_Joint(objects(n)\joint)
Next

WaitKey()

Function Create_Joint(j.joint)
      Print "jointtype="+j\joint_type
End Function

Sorry, the n was just illustrative. The code and types above are only very brief examples. In the case of my actual program, I perform the For...next initialisation loop for 50 objects, and the create_joint() function shows it's fault when referencing objects(5). This is the first object I need to create a joint for.

My fault (always is, but it helps to find faults when posted publically!). I was passing the wrong object.