How To Check if an object is created (instantiated)?

I have this simple code that I could find an answer to yet without
trigiring an exceptiom.


Type
  TMyClass = Class (tobject);
     Item : integer;
  end;


procedure Somename(Var R : TMyClass);
begin
....
  Now, inside a program how can I check to see if the Variable R has
an instance?

end;


For excample,
R := TMyClass.Create;
if you call SomeName(R)

Would be OK,

But calling  SomeName(R) without creating an instance of R ( R :=
TMyClass.Create;) would generate a fault error when R is used inside
the SomeOne procedure, so How can I check to see if the Variable "R"
was instantiated (R := TMyClass.Create;)?