Extend Itcl objects with methods inside the constructor

Question

Is there a possibility in Itcl to extend a class dynamically with methods inside the constructor?

I have some functions which are generated dynamically...

They look somehow like this:

proc attributeFunction fname {
    set res "proc $fname args {
        #set a attribute list in the class  
    }"
    uplevel 1 $res
}

Now I have a file which has a list of possible attributes:

attributeFunction ::func1
attributeFunction ::func2
attributeFunction ::func3 
...

This file gets sourced. But until now I am adding global functions. It would be way nicer to add these functions as methods to an Itcl object.

A little background information:

This is used to generate an abstract language where the user can easily add these attributes by writing them without any other keyword. The use of functions here offers a lot of advantages I do not want to miss.

Is this itcl 3 (probably 3.6) or 4? I don't know whether 3 has the ability to support this sort of thing, but the underlying technology that 4 is built on can certainly do it. Whether 4 can take advantage of it… I don't know. — Donal Fellows, Jan 17 '15 at 07:09
It is itcl 3... However is there a way in 3 and what is the new mechanism in 4? — TM90, Jan 17 '15 at 12:28

score 1 · Accepted Answer · answered Jan 17 '15 at 21:04

In Itcl 3, all you can do is redefine an existing method (using the itcl::body command). You can't create new methods in the constructor.

You can do this in Itcl 4, because is built on the foundation of TclOO (a fully dynamic OO core). You'll need the underlying TclOO facilities to do this, but the command you call is something like this:

::oo::objdefine [self] method myMethodName {someargument} {
    puts "in the method we can do what we want..."
}

Here's a more complete example:

% package require itcl
4.0.2
% itcl::class Foo {
    constructor {} {
        ::oo::objdefine [self] method myMethodName {someargument} {
            puts "in the method we can do what we want..."
        }
    }
}
% Foo abc
abc
% abc myMethodName x
in the method we can do what we want...

Looks like it works to me…

Disclosure: I wrote TclOO; I know it's capabilities intimately. :-D — Donal Fellows, Jan 17 '15 at 21:04
Actually this is awesome... But why are you sure there is not an equal mechanism underlying in itcl3? — TM90, Jan 18 '15 at 11:19

Extend Itcl objects with methods inside the constructor

1 Answers1