Data type syntax

Specify data types in your Puppet code whenever you can, aligning them in columns. Type your class parameters wherever possible, and be specific when using a type. For example, use an Enum for input validation, instead of using a String and checking the contents of the string in the code. You have the option to specify String[1] instead of String, because you might want to enforce non-empty strings. Specify data types as deeply as possible, without affecting readability. If readability becomes a problem, consider creating a custom data type alias.

Parameter lists

Classes, defined types, and lambdas all let you specify parameters, which let your code request data from a user or some other source. Generally, your code expects each parameter to be a specific kind of data. You can enforce that expectation by putting a data type before that parameter’s name in the parameter list. At evaluation time, Puppet raises an error if a parameter receives an illegal value.

class ntp (
  Boolean $service_manage = true,
  Boolean $autoupdate     = false,
  String  $package_ensure = 'present',
  # ...
) {
  # ...
}

class puppetdb::server (
  Variant[Boolean, Enum['true', 'false', 'running', 'stopped']]
    $puppetdb_service_status = $puppetdb::params::puppetdb_service_status,
) inherits puppetdb::params {
  # ...
}

Cases

$enable_real = $enable ? {
  Boolean => $enable,
  String  => str2bool($enable),
  Numeric => num2bool($enable),
  default => fail('Illegal value for $enable parameter'),
}

Match expressions

The match operators =~ and !~ accept a data type on the right operand, and test whether the left operand is a value of that data type.

For example, 5 =~ Integer and 5 =~ Integer[1,10] both resolve to true.

Less common uses

The built-in function assert_type  takes a value and a data type, and raises errors if your code encounters an illegal value. Think of it as shorthand for an if statement with a non-match (!~) expression and a fail() function call.

You can also provide data types as both operands for the comparison operators ==, !=, <, >, <=, and >=, to test whether two data types are equal, whether one is a subset of another, and so on.

Obtaining data types

The built-in function type returns the type of any value. For example, type(3) returns Integer[3,3].

For details on each data type, see the linked documentation or the specification document.

Parameters

Type[<ANY DATA TYPE>]