ValueTransformer toolkit for swift


Build Status Swift 5.1 Stargazers Issues MIT License Sponsor Become a Patron! Buy me a coffee

A closure and protocol based framework for ValueTransformer, helpful functions to register ValueTransformer by identifier.

See Some implementations

Create a ValueTransformer

Using closures

let transformer = ValueTransformer.closure { object in
   return ...

A ValueTransformer subclass is no more necessary using this method.

Using protocol implementation

Implement ValueTransformerType or ResersableValueTransformerType and an a computed property transformer will be accessible.

Using enum

Define your enum, a list of all your enum case in transformers, implement the function transformedValue of ValueTransformerType protocol

enum StringTransformers: String, ValueTransformers, ValueTransformerType {
    case capitalized, lowercased, uppercased

    public static let transformers: [StringTransformers] = [.capitalized, .lowercased, .uppercased]

    public func transformedValue(_ value: Any?) -> Any? { ../* string manipulation */ }

Register it

You can retrieve a value transformer using optional initializer of ValueTransformer: init?(forName: NSValueTransformerName)

A protocol ValueTransformerRegisterable help you to register your ValueTransformer By providing a value transformer and an identifier name, a new method will be available


So just defined an identifier name in your ValueTransformerType

struct MyTransformer: ValueTransformerType, ValueTransformerRegisterable {
    var name = NSValueTransformerName(rawValue: "MyTransformation")

For a singleton instance

You can define a singleton instance using ValueTransformerSingleton

struct MyTransformer: ValueTransformerType, ValueTransformerRegisterable, ValueTransformerSingleton {
    var name = NSValueTransformerName(rawValue: "MyTransformation")
    public static let instance = MyTransformer()

or a static function will help you to register it

MyTransformer.register() // same as MyTransformer.instance.register()

For the previous enum example

enum StringTransformers: String, ValueTransformers, ValueTransformerType {
  var name: NSValueTransformerName {
     return NSValueTransformerName("String" + self.rawValue.capitalized)

then you can register one by one


or all case


Some implementations


  • capitalized
  • uppercased
  • lowercased


  • PNG Representation
  • JPEG Representation

Date and Time

  • RFC 2822 Timestamp*
  • Using DateFormatter.Style


  • Using NumberFormatter.Style

Locale component

  • Using NSLocale.Key

Check if empty or not

  • Using IsEmpty(resp. IsNotEmpty) you could transform String, NSString, Array, NSArray, Dictionnary, etc... to boolean. true(resp. false) if empty

Apple Doc


ValueTransformerKit is available under the MIT license. See the LICENSE file for more info.


  • Swift Tools 5.0.0
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Last updated: Sat Jan 28 2023 03:02:54 GMT-0500 (GMT-05:00)