DevOps: Puppet, Docker, and Kubernetes

Passing parameters to classes

Sometimes it's very useful to parameterize some aspect of a class. For example, you might need to manage different versions of a gem package, and rather than making separate classes for each that differ only in the version number, you can pass in the version number as a parameter.

How to do it…

In this example, we'll create a definition that accepts parameters:

1. Declare the parameter as a part of the class definition:

     class eventmachine($version) {
       package { 'eventmachine': provider => gem, ensure   => $version,
       }
     }

2. Use the following syntax to include the class on a node:

     class { 'eventmachine':
       version => '1.0.3',
     }

How it works…

The class definition class eventmachine($version) { is just like a normal class definition except ...