Puppet users - Oct 2010 - How to check if a parameter is defined

Fast question:

How can I check wether a parameter is defined or not. For instance a
function that would fail (with a parser error) if the variable is not
defined:

check_defined($avar) or check_defined("$avar")

--
Atentamente
Héctor Rivas

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> How can I check wether a parameter is defined or not. For instance a
> function that would fail (with a parser error) if the variable is not
> defined:
>
> check_defined($avar) or check_defined("$avar")
I answer myself, one way would be:

   if $avar == undef { fail("''avar'' not defined") }

I think that assertions would be even better:

   assert($avar != undef)

or
   assert($avar)


I think that add assertions would be a good idea. They could check
True/False conditions, if variables are defined or not, if objects are
defined... Is there any proposal about this?

--
Atentamente
Héctor Rivas



2010/10/1 Héctor Rivas Gándara <keymon@gmail.com>:
> Fast question:
>
> How can I check wether a parameter is defined or not. For instance a
> function that would fail (with a parser error) if the variable is not
> defined:
>
> check_defined($avar) or check_defined("$avar")
>
> --
> Atentamente
> Héctor Rivas
>
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On 10/01/2010 02:30 PM, Héctor Rivas Gándara wrote:
>> How can I check wether a parameter is defined or not. For instance a
>> function that would fail (with a parser error) if the variable is not
>> defined:
>>
>> check_defined($avar) or check_defined("$avar")
> 
> I answer myself, one way would be:
> 
>    if $avar == undef { fail("''avar'' not
defined") }
> 
> I think that assertions would be even better:
> 
>    assert($avar != undef)
> 
> or
>    assert($avar)
> 
> 
> I think that add assertions would be a good idea. They could check
> True/False conditions, if variables are defined or not, if objects are
> defined... Is there any proposal about this?
I think the problem with such things is that they are dependent on the
order puppet evaluates the catalogue in, which is undefined. See

http://docs.puppetlabs.com/references/stable/function.html#defined

which does what you propose wrt. resources. An assert would be

if !defined(Resource[...]) { fail "message" }

but should not be used due to the order limitation.

Regards,
Felix

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>> I think that add assertions would be a good idea. They could check
>> True/False conditions, if variables are defined or not, if objects are
>> defined... Is there any proposal about this?
>
> I think the problem with such things is that they are dependent on the
> order puppet evaluates the catalogue in, which is undefined. See
>
> http://docs.puppetlabs.com/references/stable/function.html#defined
>
> which does what you propose wrt. resources. An assert would be
>
> if !defined(Resource[...]) { fail "message" }
> but should not be used due to the order limitation.
Well, I suppose that the assert function that I propose is just
"syntax sugar", since it can be always expressed as an
''if'' sentence.
But it could be useful to check the parameters needed in a module, for instance.

--
Atentamente
Héctor Rivas

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