On 25/02/11 20:54, Markus Roberts wrote:
> B --
>
>
> Thanks for the example. This is quite interesting and opens the door to
> a lot of strange things :)
>
>
> Yes it does. Be sure to have a big stick handy when you open that door. :)
>
>
> I was thinking about allowing the user to describe probes by specifying
> a puppet class and a method through an indirection to control probes
> (like in "Puppet::Indirector::Indirection.find"), then I'd do something
> (completely untested):
>
> method = "find"
> klass_name = "Puppet::Indirector::Indirection"
> require klass_name.split('::').map { |n| n.downcase }.join('/')
>
> klass = klass_name.split('::').inject(Puppet) { |p,c| p.const_get(c) }
> klass.class_eval do
> alias "instr_#{method}" method
> define_method(method, *args) do
> # here call to instrumentation
> send("instr_#{method}", args)
> ensure
> # here wrap up instrumentation
> end
> end
>
> Then I hope, somewhere else, someone calling Puppet::Something.find
> (provided Something uses the indirector of course), then it would call
> my programmatic redifinition of "find"...
>
>
> Yikes.
>
>
> This will be a funny week-end if that proves to work :)
>
>
> Yeah, it will. A few thoughts:
>
> 1) alias takes an identifier, not a string, so you'll have to use
> alias_method (which also needs a coma between the arguments).
> 2) you have to be careful with interpolation, in any case, as there are
> scope changes to watch out for.
Can you elaborate on this?
> 3) class_eval/define_method add quite a few wrinkles over class/def
> (which are after all executable, and can be run dynamically).
It doesn't seem possible to say:
def <code here that gives a method name>
end
So I'll have to use define_method.
I'm also concerned by the performance penalty paid when redefining a
method like this...
> Good luck, & feel free to ping me if you hit a snag.
I will certainly do :)
--
Brice Figureau
My Blog: http://www.masterzen.fr/
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