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undef variable

asked 2017-03-23 14:28:21 -0600

WiktorVip gravatar image

Hello All I have puppet master in 3.8 version. I need part of code for undefined variable. Example: if var is undefined setup some value something like this but is not working.

if $my_parameter  == 'undef' {
  $my_parameter = 'none'

if variable is defined don't change it

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PP is not a procedural language. All “variables” have a final value with their first assignment. Also you're comparing against the string 'undef'. You want to check against the literal undef (not surrounded by single quotes).

Kai Burghardt gravatar imageKai Burghardt ( 2017-03-23 17:15:24 -0600 )edit

I made only example what I need.. there is no any way to make condition like this?

WiktorVip gravatar imageWiktorVip ( 2017-03-24 06:35:51 -0600 )edit

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answered 2017-03-24 06:36:57 -0600

puser gravatar image

updated 2017-03-24 06:40:45 -0600

if $myparameter == undef { $myparameter = 'none' }

p.s. If I was the manager of whoever wrote this code they would get a talking to.

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answered 2017-03-24 07:13:22 -0600

DarylW gravatar image

The pattern that I most commonly see for this type of 'workflow' internal to a module (not across module boundries) is to use _ to prefix a private variable.

class foo (
  $optional_param = undef,
  # either using a selector to set a 'default' value, usually used if I am munging multiple params, or if one potential default value depends on a different param (like paths relative to a base path)
  $_optional_param = $optional_param ? {
    undef          => 'none',
    default            => $optional_param,

Or more generally, just use a default. value, and conditionally assign a different parameter to use in a different location that 'requires' undef.

class bar (
  # Or just use a default value explicitly
  $optional_param = 'none',
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Asked: 2017-03-23 14:28:21 -0600

Seen: 2,587 times

Last updated: Mar 24 '17