Re: [Tclxml-users] itcl/tk-like calling syntax for TclDom

[Steve B. <Ste...@zv...>]

On 15/09/2004, at 12:37 AM, Detlef Groth wrote:

> I like the itcl/tk- and Tdom-like calling conventions for tdom:

TclDOM version 3.0 has introduced that style of API, but not uniformly 
throughout the package (yet).

At the time that I was implementing this feature I had an issue with 
overloading the document/node commands with methods for multiple node 
classes.  For example, an element node is both a Node and an Element 
class object, so should have the methods for both the ::dom::node and 
::dom::element commands.  However, a TextNode or a Document node will 
have a different set a methods.

> (tclkit) 82 % set doc [dom::DOMImplementation create]
> ::dom::tcl::document7::Document
> (tclkit) 83 % set top [dom::document createElement $doc html]
> ::dom::tcl::document7::node2
> (tclkit) 84 % set title [$doc createElement title]
> ::dom::tcl::document7::node6
> (tclkit) 85 % $top appendChild $title
> ::dom::tcl::document7::node6
> (tclkit) 86 % set body [$doc createElement body]
> ::dom::tcl::document7::node13
> (tclkit) 87 % $top appendChild $body
> ::dom::tcl::document7::node13
> (tclkit) 88 % $body setAttribute bgcolor black
> unknown method "setAttribute"
>
> This does not work, however this:
>
> (tclkit) 90 % dom::element setAttribute $body bgcolor black
> black

Yes, that exactly the issue raised above.  "setAttribute" is a method 
of the ::dom::element command.  You'd like to be able to do:

$body setAttribute bgcolor black

What happens if you do:

$doc setAttribute bgcolor black

The latter should probably throw an exception.

Making the former work would mean either defining the node command as a 
separate function and implementing every method from every node class 
command (for both Tcl and libxml2), or modifying the node command to 
call the class-specific function if the method is not defined 
(actually, the latter would be the best approach).

> which is for me a little bit awkward, and I always forget to add the
> nodename after the (get|set)Attribute-command. I am used to javascript
> where we say something like:
>
> var input = window.document.createElement("input");
> input.setAttribute("name", "inputvalue");

Having to remember to add the node token does make the API a bit 
awkward, I agree.

> It should be not to difficult to write some simple wrapper classes
> with Snit or something similar. But using snit may slow down the code. 
> Did
> anyone have a better suggestion?

Do it in the TclDOM package itself; please submit a feature request to 
SF.

At the moment I'm flat-out with other (paid-for) projects so I won't be 
able to do anything about it in the short-term.  However, maybe someone 
else will step up to the plate and give it a go.

>  As a side effect the same code might run with tdom also.

Ah... that's a sore point.  You go talk to the tDOM people about 
compatibility :-(

Cheers,
Steve Ball

---

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