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A block-based API for NSValueTransformer, with a growing collection of useful examples.


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A block-based API for NSValueTransformer, with a growing collection of useful examples.

NSValueTransformer, while perhaps obscure to most iOS programmers, remains a staple of OS X development. Before Objective-C APIs got in the habit of flinging block parameters hither and thither with reckless abandon, NSValueTransformer was the go-to way to encapsulate mutation functionality --- especially when it came to Bindings.

NSValueTransformer is convenient to use but a pain to set up. To create a value transformer you have to create a subclass, implement a handful of required methods, and register a singleton instance by name.

TransformerKit breathes new life into NSValueTransformer by making them dead-simple to define and register:

NSString * const TTTCapitalizedStringTransformerName = @"TTTCapitalizedStringTransformerName";

[NSValueTransformer registerValueTransformerWithName:TTTCapitalizedStringTransformerName
                               transformedValueClass:[NSString class]
                  returningTransformedValueWithBlock:^id(id value) {
  return [value capitalizedString];

TransformerKit pairs nicely with InflectorKit and FormatterKit, providing well-designed APIs for manipulating user-facing content.

TransformerKit also contains a growing number of convenient transformers that your apps will love and cherish:

String Transformers

  • Capitalized
  • lowercase
  • CamelCase
  • llamaCase
  • snake_case
  • train-case
  • esreveR* (Reverse)
  • Rémövê Dîaçritics (Remove accents and combining marks)
  • ट्रांस्लितेराते स्ट्रिंग (Transliterate to Latin)
  • Any Valid ICU Transform*

Image Transformers

  • PNG Representation*
  • JPEG Representation*
  • GIF Representation (macOS)
  • TIFF Representation (macOS)

Date Transformers

JSON Data Transformers

  • JSON Transformer*

Data Transformers (macOS)

  • Base16 String Encode / Decode
  • Base32 String Encode / Decode
  • Base64 String Encode / Decode
  • Base85 String Encode / Decode

Cryptographic Transformers (macOS)

  • MD5, SHA-1, SHA-256, et al. Digests

* - Reversible


Mattt (@mattt)


TransformerKit is released under the MIT license. See the LICENSE file for more info.