---
title: applinks.SubstitutionVariables
framework: bundleresources
role: symbol
role_heading: Object
path: bundleresources/applinks/substitutionvariables-swift.dictionary
---

# applinks.SubstitutionVariables

A list of named strings and an associated array of string values that define custom substitution variables to use for URL pattern matching.

## Declaration

```swift
object applinks.SubstitutionVariables
```

## Properties

Any Key:

## Discussion

Discussion The keys in this object are substitution variable names; the value for each key is an array of strings to substitute for the associated variable in URL pattern-matching operations. The names you use for substitution variables are always case-sensitive and can contain any character except $, (, and ). The values you use with substitution variables are case-sensitive by default and can contain the ? and * wildcard characters, but not other substitution variables. The following is a list of predefined substitution variables and examples of each: $(alpha) — All upper- and lowercase ASCII letters of the alphabet: A, a, B, b, C, c, …, Z, z. $(upper) — All uppercase ASCII letters of the alphabet: A, B, C, …, Z. $(lower) — All lowercase ASCII letters of the alphabet: a, b, c, …, z. $(alnum) — All alphanumeric ASCII characters: A, a, …, Z, z, 0, …, 9. $(digit) — All decimal digits: 0, …, 9. $(xdigit) — All hexadecimal digits: 0, …, F, f. $(region) — All ISO regions in isoRegionCodes, such as CA, UK, and US. $(lang) — All ISO languages in isoLanguageCodes, such as ar, en, and zh. This example code shows how to use universal links substitution variables in an association file: {   "applinks": {     "substitutionVariables": {       "food": [ "burrito", "pizza", "sushi", "samosa" ]     },     "details": [{       "appIDs": [ ... ],       "components": [         { "/" : "/$(lang)_$(region)/$(food)/" }       ]     }]   } }