The following code is somewhat experimental. I have seen quite a few variations on this theme. However, I believe this code does things in a new and interesting way. This code is not feature complete, it is primarily a proof of concept at this point. Please feel free to make comments and/or criticize this code. If you have feature/code suggestions please feel free to add them to this page. If you would like to submit code changes, please email them to me and I will review them for addition.
This code allows for the following concepts/constructs:
- "classes" definitions or "what procs and variables do all instances of this class have?"
- "objects" or "an instance of a class."
- Now supports transparent usage of class variables and procs from inside the class.
- "interfaces" or "what procs are required to implement this interface?"
- "comment" blocks inside class and interface declarations.
- "options" or "what optional features are enabled for this class or interface?"
- "single inheritance" or "procs from this other class are now in this class."
- "multiple inheritance" or "procs from these other classes are now in this class."
- "nested inheritance" or "procs from the base of my base are now in this class."
- "constructors" and "destructors", that can take parameters and can prevent the object from being created/destroyed.
The only "missing" things that I can think of so far are:
- Being able to delegate a method to one of your bases.
- A nice way to handle "conflicts" between procs in the immediate class and the bases (perhaps in more than one base). Currently, if a proc exists in the immediate class, it is always called. The result of calling a non-qualified proc that exists in more than one base class is undefined.
- The ability to control access to the procs of a class (public, private, etc).
This code is now too big for a WiKi page (about 100K, including test files).
It may be downloaded from: http://www.tclbridge.com/tcl_oo.zip
Here's a simple example of how to declare and use a class with this OO system...
class demoClass {
option alias.primary
option proc.trace.outer
option proc.trace.inner
variable x
variable y
variable z
variable array_variable
comment {
#
# override global proc locally...
# (notice we call the global proc from inside it)
#
}
proc class_output { output } {
::class_output "$this: $output"; # calls global proc
}
proc constructor { object args } {
class_output "NEW: $this"; return "1"
}
proc destructor { object args } {
class_output "DELETE: $this"; return "1"
}
proc doNothing {a} {}
proc simpleReturn {} { return $x.$y }
proc returnMethod {a} { return [doNothing $a] }
proc callMethod {a} { $this doNothing $a; return $x }
proc testArray {} {
set array_variable(1) "element1"
set array_variable(2) "element2"
set array_variable(3) "element3"
return [array names array_variable]
}
}
Written By Joe Mistachkin
Version History
- 19/Nov/2002 Version 1.00 -- initial release.
- 19/Nov/2002 Version 1.20 -- added transparent access to class variables.
- -- streamlined some of the code.
- -- more comprehensive cleanup of variables, procs, and namespaces.
- 20/Nov/2002 Version 1.25 -- more robust handling of invalid class declarations.
- -- added tests for arrays inside classes.
- 20/Nov/2002 Version 1.30 -- more argument validation.
- -- added more tests dealing with invalid class declarations.
- -- added class_objects proc to return a list of active objects for a class.
- 20/Nov/2002 Version 1.31 -- fixed error handling for a certain test case involving bad class declarations.
- 20/Nov/2002 Version 1.32 -- fixed problem preventing multiple matches in class_objects.
- 22/Nov/2002 Version 1.40 -- added support for interfaces.
- -- added support for comment blocks inside classes and interfaces.
- -- cleaned up and organized tests.
- -- changed some error messages.
- -- other miscellaneous changes.
- 13/Mar/2003 Version 1.60 -- added support for inheritance, single and multiple.
- -- a lot of cleanup and reorganization.
- -- added support for implementing an interface using base classes.
- -- added more introspection features.
- -- added support for parameterized constructors/destructors (can stop creation/destruction).
- 13/Mar/2003 Version 1.61 -- corrected loop invariant for interface definitions.
- 15/Mar/2003 Version 1.75 -- massive internal changes to namespace handling.
- -- added support for nested inheritance.
- -- added first stages of "conflict resolution" (currently, there is none).
- -- cleaned up class_hasProc.
- -- massively changed and streamlined class_findProc.
- -- added more introspection commands.
- -- added more tests to "class_test2.tcl".
- 16/Mar/2003 Version 1.89 -- more massive changes to namespace handling.
- -- added support for class and interface "options".
- -- removed some old dead code.
- -- changed proc aliasing to be more robust, aliases are now visible within the namespace of the calling object only.
- -- added support for a variable number of arguments to procs defined with an "args" parameter as the last parameter.
Category Object Orientation