swift-casification

Package for tokenizing and applying case transformations to arbitrary strings.

Table of contents

• Motivation
• Usage
  • Basic modifiers
  • Token-based modifiers
  • Composing modifiers
  • Custom modifiers
• Installation
• License

Motivation

Swift does not provide a standard way to tokenize strings or to build formatted strings from such tokens.

As a result, even common transformations like camelCase are often implemented differently across projects, leading to duplicated logic and inconsistent results.

This package focuses on providing a set of predefined, reusable string modifiers for common casing and formatting transformations, with consistent behavior across codebases.

Usage

A set of predefined string modifiers is available out of the box

Basic modifiers

Modifiers	Examples
upper	string → STRING
lower	STRING → string
upperFirst	String → String
lowerFirst	STRING → sTRING
capital	some string → Some String
swap	Some String → sOME sTRING

Token-based modifiers

Those modifiers are a bit more complex and do support configuration

• String.Casification.PrefixPredicate allows configuring allowed prefixes, .swiftDeclarations is used by default allowing $ and _ symbols for prefixes
• You can also provide a list of acronyms. The default list is available at String.Casification.standardAcronyms, there is no way to modify this list at least yet, but you can explicitly specify your own, we'll add modification mechanism in future versions of the library.

Modifiers	Examples
camel(.camel)	some string → someString
camel(.pascal)	some string → SomeString
camel	some string → someString
pascal	some string → SomeString
camel(.automatic)	some string → someString
camel(.automatic)	Some string → SomeString
snake()	some string → some_string
kebab()	some string → some-string
dot()	some string → some.string

Note

See Tests for more examples

Composing modifiers

Modifiers can be combined using combined(with:) method. Order matters – transformations are applied sequentially.

// "myString" → "mystring" → "Mystring"
"myString".case(.lower.combined(with: .upperFirst))

// "myString" → "Mystring" → "mystring"
"myString".case(.upperFirst.combined(with: .lower)) // mystring

Custom modifiers

For simple modifiers, conforming a type to String.Casification.Modifier is enough

extension String.Casification.Modifiers {
  /// Deletes input string
  public struct Delete: String.Casification.Modifier {
    public init() {}
    
    @inlinable 
    public func transform(_ input: Substring) -> Substring {
      ""
    }
  }
}

Tip

It's a good idea to declare convenience accessor for the protocol

extension String.Casification.Modifier
where Self == String.Casification.Modifiers.Delete {
     public var delete: Self { .init() }
}

"myString".case(.delete) // ""

For more complex processing, you can operate on tokens instead of raw strings by conforming to String.Casification.TokensProcessor

extension String.Casification.TokensProcessors {
  public struct RemoveSeparators: String.Casification.TokensProcessor {
    public init() {}
    @inlinable
    public func processTokens(
      _ tokens: ArraySlice<String.Casification.Token>
    ) -> ArraySlice<String.Casification.Token> {
      return filter { $0.kind != .separator }[...]
    }
  }
}

extension String.Casification.Modifier
where Self == String.Casification.Modifier.ProcessingTokens<
  String.Casification.TokensProcessors.RemoveSeparators
>{
  public var noSeparators: Self {
    .init(using: .init())
  }
}

"my test-string".case(.noSeparators) // "myteststring"

Note

The package is primarily designed around predefined reusable modifiers. Custom modifiers are supported, but declarations can be verbose due to namespacing and generic types.

Installation

Basic

You can add Casification to an Xcode project by adding it as a package dependency.

1. From the File menu, select Swift Packages › Add Package Dependency…
2. Enter "https://github.com/capturecontext/swift-casification.git" into the package repository URL text field
3. Choose products you need to link them to your project.

Recommended

If you use SwiftPM for your project, you can add Casification to your package file.

.package(
  url: "https://github.com/capturecontext/swift-casification.git", 
  .upToNextMinor(from: "0.1.0")
)

Do not forget about target dependencies:

.product(
  name: "Casification", 
  package: "swift-casification"
)

License

This library is released under the MIT license. See LICENSE for details.