Introduction

Supporting XOTcl 1 in Next

In general, the Next environment supports multiple object systems concurrently. Effectively, every object system has different base classes for creating both, objects and classes. Therefore, the object systems can have different different interfaces and names of builtin methods. Currently, Next supports primarily XOTcl and the Next scripting language (XOTcl provides about twice as many predefined builtin methods compared to Next).

A single Tcl interpreter can host both, XOTcl and the Next scripting language at the same time. This makes migration from XOTcl to Next easier. The following example script shows to use in a single XOTcl and Next

   namespace eval mypackage {

      package require XOTcl

      # Import XOTcl into the current namespace
      namespace import -force ::xotcl::*

      # Define a class using XOTcl
      Class C1
      C1 instproc foo {} {puts "hello world"}

      # Import Next into the current namespace
      namespace import -force ::nx::*

      # Define a class using Next
      Class create C2 {
         :method foo {} {puts "hello world"}
      }
   }

"Switching" between XOTcl and Next effectively means the load some libraries if needed and to import either the base classes (Object and Class) of XOTcl or Next into the current namespace.

XOTcl Idioms in the Next scripting language

Defining Objects and Classes

Defining Methods

Resolvers

Invoking Methods

Accessing Instance Variables from Method Bodies

Accessing Instance Variables of other Objects

Object Parameters

Method Parameters

Introspection

List methods defined by objects

List methods defined by classes

List class object specific methods

List callable methods

List object/class where some method is defined

List definition of scripted methods defined by classes

List definition of scripted object specific methods

For definition of class object specific methods, use modifier object as shown in examples above.

List filter or mixins

List definition of methods defined by aliases, setters or forwarders

List fully qualified name of method

List type of a method

List the scope of mixin classes

Check properties of object and classes

Predefined Methods

Dispatch, Aliases, etc.

Assertions

Method Protection

Incompatibilities

Namespace resolvers

The Next namespace resolvers are use as well when XOTcl is used within Next.

Stronger Checking

Next performs stronger checking than XOTcl. The requiredness of slots in XOTcl was just a comment, while Next enforces it.

Different results

• [self next] returns
  instead of "proc" and "instproc" => "method"
  instead of "parametercmd" and "instparametercmd" => "setter"
  instead of "instforward" => "forward"
  instead of "instcmd" => "cmd".
  The modifier "object" is added when needed.
• [self filterreg] returns
  instead of "instforward" => "forward"
  The modifier "object" is added when needed.

Exit handlers

The exit hander interface changed from a method of ::xotcl::Object into procs in the ::nx::core namespace. Next provides now:

   ::nx::core::setExitHandler script
   ::nx::core::getExitHandler
   ::nx::core::unsetExitHandler