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filters-strings.md

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Filters

This is a list of filters that are added by StencilSwiftKit on top of the filters already provided by Stencil (which you can find here).

Filter: basename

Get the last component of a path, essentially the filename (and extension).

Input Output
test.jpg test.jpg
some/folder/test.jpg test.jpg
file.txt.png file.txt.png

Filter: camelToSnakeCase

Transforms text from camelCase to snake_case. The filter accepts an optional boolean parameter:

  • true (default): Lowercase each component.
  • false: Keep the casing for each component.
Input Output (true) Output (false)
SomeCapString some_cap_string Some_Cap_String
someCapString some_cap_string some_Cap_String
String_With_WoRds string_with_words String_With_Wo_Rds
string_wiTH_WOrds st_ring_with_words string_wi_TH_W_Ords
URLChooser url_chooser URL_Chooser
PLEASE_STOP_SCREAMING please_stop_screaming PLEASE_STOP_SCREAMING

Filter: contains

Checks if the string contains given substring - works the same as Swift's String.contains.

Input Output
Hello el true
Hi mates! yo false

Filter: dirname

Remove the last component of a path, essentially returning the path without the filename (and extension).

Input Output
test.jpg ``
some/folder/test.jpg some/folder
file.txt.png ``

Filter: escapeReservedKeywords

Checks if the given string matches a reserved Swift keyword. If it does, wrap the string in escape characters (backticks).

Input Output
hello hello
self `self`
Any `Any`

Filter: hasPrefix

Checks if the string has the given prefix - works the same as Swift's String.hasPrefix.

Input Output
Hello Hi false
Hi mates! H true

Filter: hasSuffix

Checks if the string has the given suffix - works the same as Swift's String.hasSuffix.

Input Output
Hello llo true
Hi mates! ? false

Filter: lowerFirstLetter

Simply lowercases the first character, leaving the other characters untouched.

Input Output
Hello hello
PeopleChooser peopleChooser
Hi There! hi There!

Filter: lowerFirstWord

Transforms an arbitrary string so that only the first "word" is lowercased.

  • If the string starts with only one uppercase character, lowercase that first character.
  • If the string starts with multiple uppercase character, lowercase those first characters up to the one before the last uppercase one, but only if the last one is followed by a lowercase character. This allows to support strings beginnng with an acronym, like URL.
Input Output
PeoplePicker peoplePicker
URLChooser urlChooser

Filter: replace

This filter receives at least 2 parameters: a search parameter and a replacement. This filter has a couple of modes that you can specify using an optional mode argument:

  • normal (default): Simple find and replace.
  • regex: Enables the use of regular expressions in the search parameter.
Input (search, replacement) Output (normal) Output (regex)
Hello (l, k) Hekko Hekko
Europe (e, a) Europa Europa
Hey1World2! (\d, ) Hey1World2! Hey World !

Filter: snakeToCamelCase

Transforms a string in "snake_case" format into one in "camelCase" format, following the steps below:

  • Separate the string in components using the _ as separator.
  • For each component, uppercase the first character and do not touch the other characters in the component.
  • Join the components again into one string.

If the whole starting "snake_case" string only contained uppercase characters, then each component will be capitalized: uppercase the first character and lowercase the other characters.

This filter accepts an optional boolean parameter that controls the prefixing behaviour:

  • false (default): don't remove any empty components.
  • true: trim empty components from the beginning of the string
Input Output (false) Output (true)
snake_case SnakeCase SnakeCase
snAke_case SnAkeCase SnAkeCase
SNAKE_CASE SnakeCase SnakeCase
__snake_case __SnakeCase SnakeCase

Filter: 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). It will apply the following rules:

  • Uppercase the first character.
  • Prefix with an underscore if the first character is a number.
  • Replace invalid characters by an underscore (_).

The list of allowed characters can be found here: https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html

This filter has a couple of modes that you can specify using an optional mode argument:

  • valid: Only do the bare minimum for a valid identifier, i.e. the steps mentioned above except uppercasing characters.
  • normal (default): apply the steps mentioned above (uppercase first, prefix if needed, replace invalid characters with _).
  • pretty: Same as normal, but afterwards it will apply the snakeToCamelCase filter, and other manipulations, for a prettier (but still valid) identifier.
Input Output (valid) Output (normal) Output (pretty)
hello hello Hello Hello
42hello _42hello _42hello _42hello
some$URL some_URL Some_URL SomeURL
25 Ultra Light _25_Ultra_Light _25_Ultra_Light _25UltraLight
26_extra_ultra_light _26_extra_ultra_light _26_extra_ultra_light _26ExtraUltraLight
apples.count apples_count Apples_Count ApplesCount
foo_bar.baz.qux-yay foo_bar_baz_qux_yay Foo_bar_Baz_Qux_Yay FooBarBazQuxYay

Filter: titlecase

Deprecated in favor of upperFirstLetter.

Filter: upperFirstLetter

Simply uppercases the first character, leaving the other characters untouched.

Note that even if very similar, this filter differs from the capitalized filter, which uppercases the first character but also lowercases the remaining characters.

Input Output
hello Hello
peopleChooser PeopleChooser