A framework bringing additional nodes & filters to Stencil dedicated to Swift code generation


CircleCI CocoaPods Compatible Platform Swift 3.0

StencilSwiftKit is a framework bringing additional Stencil nodes & filters dedicated to Swift code generation.


  • Macro & Call
    • {% macro <Name> <Params> %}…{% endmacro %}
    • Defines a macro that will be replaced by the nodes inside of this block later when called
    • {% call <Name> <Args> %}
    • Calls a previously defined macro, passing it some arguments
  • Set
    • {% set <Name> %}…{% endset %}
    • Renders the nodes inside this block immediately, and stores the result in the <Name> variable of the current context.
  • Map
    • {% map <Variable> into <Name> using <ItemName> %}…{% endmap %}
    • Apply a map operator to an array, and store the result into a new array variable <Name> in the current context.
    • Inside the map loop, a maploop special variable is available (akin to the forloop variable in for nodes). It exposes maploop.counter, maploop.first, maploop.last and maploop.item.


  • String filters:
    • basename: Get the filename from a path.
    • camelToSnakeCase: Transforms text from camelCase to snake_case. By default it converts to lower case, unless a single optional argument is set to "false", "no" or "0".
    • contains: Check if a string contains a specific substring.
    • dirname: Get the path to the parent folder from a path.
    • escapeReservedKeywords: Escape keywords reserved in the Swift language, by wrapping them inside backticks so that the can be used as regular escape keywords in Swift code.
    • hasPrefix / hasSuffix: Check if a string starts/ends with a specific substring.
    • lowerFirstLetter: Lowercases only the first letter of a string.
    • lowerFirstWord: Lowercases only the first word of a string.
    • removeNewlines: Removes newlines and other whitespace characters, depending on the mode ("all" or "leading").
    • replace: Replaces instances of a substring with a new string.
    • snakeToCamelCase: Transforms text from snake_case to camelCase. By default it keeps leading underscores, unless a single optional argument is set to "true", "yes" or "1".
    • swiftIdentifier: Transforms an arbitrary string into a valid Swift identifier (using only valid characters for a Swift identifier as defined in the Swift language reference). In "pretty" mode, it will also apply the snakeToCamelCase filter afterwards, and other manipulations if needed for a "prettier" but still valid identifier.
    • upperFirstLetter: Uppercases only the first character
  • Number filters:
    • int255toFloat
    • hexToInt
    • percent


This framework also contains a StencilSwiftTemplate class, which is a subclass of Stencil.Template dedicated to remove extra newlines when rendering the template.

Indeed, such extra newlines could otherwise be inserted in the generated output because you want your template to be well formatted, and that can end up with Stencil nodes like {% for … %} and {% if … %} be alone in some lines of your template and that would render into nothing by themselves, generating empty lines in the output.

This template subclass aims to remove those lines generated by using a simple workaround when rendering, until there's an embeded way to handle that in Stencil proper (see Stencil/#22).

Stencil.Extension & swiftStencilEnvironment

This framework also contains helper methods for Stencil.Extension and Stencil.Environment, to easily register all the tags and filters listed above on an existing Stencil.Extension, as well as to easily get a Stencil.Environment preconfigured with both those tags & filters Extension and the StencilSwiftTemplate.


This framework contains an additional parser, meant to parse a list of parameters from the CLI. For example, using Commander, if you receive a [String] from a VariadicOption<String>, you can use the parser to convert it into a structured dictionary. For example:

["foo=1", "bar=2", "baz.qux=hello", "baz.items=a", "baz.items=b", "something"]

will become

  "foo": "1",
  "bar": "2",
  "baz": [
    "qux": "hello",
    "items": [
  something: true

For easier use, you can use the StencilContext.enrich(context:parameters:environment:) function to add the following variables to a context:

  • param: the parsed parameters using the parser mentioned above.
  • env: a dictionary with all available environment variables (such as PATH).


  • Swift Tools 4.0.0
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Last updated: Mon Jan 30 2023 23:33:54 GMT-0500 (GMT-05:00)