Type aliases allow you to create reusable and descriptive data and resource types.
Creating type aliases
Type aliases are written as:
type <ALIAS NAME> = <TYPE DEFINITION>
<ALIAS NAME> begins with a capital letter and must not be a reserved word.
For example, you can create a type alias named
MyType that is equivalent to the
Integer data type:
type MyType = Integer
You can then declare a parameter using the alias as though it were a unique data type:
MyType $example = 10
By using type aliases, you can:
- Give a type a descriptive name, such as
IPv6Addr, instead of creating or using a complex pattern-based type.
- Shorten and move complex type expressions.
- Improve code quality by reusing existing types instead of inventing new types.
- Test type definitions separately from manifests.
Type alias transparency
Type aliases are transparent, which means they are fully equivalent to the types of which they are aliases. For instance, this example’s
MyType is an alias of the
type MyType = Integer notice MyType == Integer
Note: The internal types
TypeAliasare never values in Puppet code.
Organizing type alias defintiions
If you define type aliases inside of manifests that contain other Puppet code, you make it more difficult to find where and how they are defined. It’s easier to maintain and diagnose problems with type aliases by placing them into files within their own directory of your Puppet module.
Store type aliases as
.pp files in your module’s
types directory, which is a top-level directory and sibling of the
lib directories. Define only one alias per file, and name the file after the type alias name converted to lowercase. For example,
MyType is expected to be loaded from a file named
Creating recursive types
You can create recursive types:
type Tree = Array[Variant[Data, Tree]]
Tree type alias is defined as a being built out of Arrays that contain Data, or a Tree:
[1,2 , [4, [5, 6], [[[[1,2,3]]]]]]
A recursive alias can refer to the alias being declared, or to other types.
This powerful mechanism allows you to define complex, descriptive type definitions instead of using the
Aliasing resource types
You can also create aliases to resource types.
type MyFile = File
When defining an alias to a resource type, use its short form (such as
File) instead of its long form (such as