check if handler exist before using it

Richard Gaskin ambassador at
Fri Nov 9 10:51:35 CST 2007

Thierry wrote:
> As I'm doing  an administration tool, I have to take care
> of  differents scenarios , so for instance,
> having to deal with protected scripts which I didn't write myself,
> and without the password....

You may be able to use "try" to see if a "handler not found" error is 

In circumstances where I have control over the stacks being queried I've 
used a custom prop containing a list of "public" handlers for easy 
access by other scripts.  It does require an extra step to create that 
list, but it can be automated during development with a 
handler-collecting function like the one Mark Schonewille listed.

But I must admit that the circumstances in which such a mechanism was 
useful have been very rare for me.   How often do you need to call a 
handler without knowing whether it's present?

Usually in my own work I find that I can implement conditional behaviors 
more easily with property settings, so merely querying the customKeys of 
an object tells me what I need to know, without having to resort to a 
handler list among them.

Finding the best solution for your circumstance will of course require 
that we know a bit more about it.  Can you describe the setup for us?

  Richard Gaskin
  Managing Editor, revJournal
  Rev tips, tutorials and more:

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