5.23.4.3 The oof.fs base class

When you define a class, you have to specify a parent class. So how do you start defining classes? There is one class available from the start: object. You have to use it as ancestor for all classes. It is the only class that has no parent. Classes are also objects, except that they don’t have instance variables; class manipulation such as inheritance or changing definitions of a class is handled through selectors of the class object.

object provides a number of selectors:

• class for subclassing, definitions to add definitions later on, and class? to get type informations (is the class a subclass of the class passed on the stack?).

  class       "name" –         oof       “class”
  

  definitions       –         oof       “definitions”
  

  class?       o – flag         oof       “class-query”
  

• init and dispose as constructor and destructor of the object. init is invocated after the object’s memory is allocated, while dispose also handles deallocation. Thus if you redefine dispose, you have to call the parent’s dispose with super dispose, too.

  init       ... –         oof       “init”
  

  dispose       –         oof       “dispose”
  

• new, new[], :, ptr, asptr, and [] to create named and unnamed objects and object arrays or object pointers.

  new       – o         oof       “new”
  

  new[]       n – o         oof       “new-array”
  

  :       "name" –         oof       “define”
  

  ptr       "name" –         oof       “ptr”
  

  asptr       o "name" –         oof       “asptr”
  

  []       n "name" –         oof       “array”
  

• :: and super for explicit scoping. You should use explicit scoping only for super classes or classes with the same set of instance variables. Explicitly-scoped selectors use early binding.

  ::       "name" –         oof       “scope”
  

  super       "name" –         oof       “super”
  

• self to get the address of the object

  self       – o         oof       “self”
  

• bind, bound, link, and is to assign object pointers and instance defers.

  bind       o "name" –         oof       “bind”
  

  bound       class addr "name" –         oof       “bound”
  

  link       "name" – class addr         oof       “link”
  

  is       xt "name" –         oof       “is”
  

• ' to obtain selector tokens, send to invocate selectors form the stack, and postpone to generate selector invocation code.

  '       "name" – xt         oof       “tick”
  

  postpone       "name" –         oof       “postpone”
  

• with and endwith to select the active object from the stack, and enable its scope. Using with and endwith also allows you to create code using selector postpone without being trapped by the state-smart objects.

  with       o –         oof       “with”
  

  endwith       –         oof       “endwith”