Thanks for the feedback. I do see the same behavior and I no longer need to
do this but I am confused by your suggestion to not use += even though it's
a valid Puppet capability.
My simplified example was actually based on a parameterized activemq class.
In my MCollective server's node definition I'd have
class { "activemq": application => "mcollective" }
while in another regex-based node definition, based on requirements of a
team I help support (called Transform for short), I'd have
class { "activemq": application => "transform" }
Then in the activemq class I wanted to specify the list of packages to
install for activemq, leaving out the java package since the Transform
systems would already have java installed separately. Hence I'd have a
single list of packages with a += if $application == "transform". The +=
was to avoid repetition of package names. You mention hacking something
together with inline_template and split (which I've used in other
situations), but I was shooting for a more elegant solution.
Justin
On Wed, Nov 16, 2011 at 6:22 AM, jcbollinger <john.bollin...@stjude.org>wrote:
>
>
> On Nov 15, 3:42 pm, Justin Lloyd <jstn...@gmail.com> wrote:
> > I tried the following (names changed to protect the innocent and guilty):
> >
> > class myclass ( $param ) {
> >
> > $myvar = [ "foo", "bar" ]
> >
> > if $param == "special" {
> > $myvar += [ "blah" ]
> > }
> >
> > }
> >
> > and got the message "...Cannot append, variable myvar is defined in this
> > scope...". According to the docs, variables cannot be modified in the
> same
> > scope because of the declarative nature of
> > Puppet<http://docs.puppetlabs.com/guides/language_guide.html>
> > .
> >
> > However, if I change the plus-signment statment to
> >
> > $myclass::myvar += [ "blah" ]
> >
> > it works fine. Can someone explain this aspect of scoping? (Or is this
> > possibly a bug...?)
>
>
> Do check whether you are seeing the behavior Christopher reports.
>
> It is a Puppet axiom that you cannot modify the value of any variable
> once it is set. Even += doesn't really do that: that's why the
> appended values are not seen outside the scope where the += is
> performed.
>
> I recommend you just come up with another way to do what you want. In
> fact, I recommend you avoid += even in situations where it works.
> Here's one way:
>
> class myclass ( $param ) {
> if $param == "special" {
> $myvar = [ "foo", "bar", "blah" ]
> } else {
> $myvar = [ "foo", "bar" ]
> }
> }
>
> There are also a couple of ways you could concatenate arrays in
> Puppet. If you want to do that a lot then I'd write a custom
> function, but for the odd one-off you could hack together something
> using inline_template() and split().
>
>
> John
>
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