Transformers

Here we define an interface for Transformers as well as an Abstract class from which concrete objects that transform data based on field names can be built. The goal: to standardize the way that Dash creates transformers in their work.

Installation

composer require dashifen/transformer

Usage

You can either extend the AbstractTransformer object or simply implement the TransformerInterface on your own. The interface defines two methods:

1. canTransform - returns a Boolean value to tell the calling scope if data can be transformed based on a $field parameter.
2. transform - returns a transformed $value based on a $field parameter.

The AbstractTransformer implements both of these for you while requiring that you define a third method: a protected getTransformationMethod method. It returns the name of another method that is assumed to be of the same object that can transform data labeled by $field.

Example

In this example, we're assuming that the naming convention for the application's fields is to use kebab-case.

class Transformer extends AbstractTransformer {
    protected function getTransformationMethod(string $field): string {
      
        // to convert a kebab-case $field to a function name, we want to 
        // convert it to StudlyCaps.  so, first, we convert from kebab-case to 
        // camelCase and then we ucfirst() the camelCase string to make it 
        // studly.  finally, we add the word "transform."  Thus, a start-date
        // field becomes startDate, then StartDate, and finally we return 
        // transformStartDate.
  
        $camelCase = preg_replace_callback("/-([a-z])/", function (array $matches): string {
            return strtoupper($matches[1]);
        }, $field);
      
        return "transform" . ucfirst($camelCase);
    }

    private function transformStartDate(string $date): string {
      
        // we assume that $date has already been validated, so here we just
        // want to make sure it's in YYYY-MM-DD format.  strtotime() can help
        // with that!
  
        return date("Y-m-d", strtotime($date));
    }
}

The above little class represents a simple, concrete object based on the functionality of the AbstractTransformer found within this repo. The abstract object's implementation of the canTransform and transform methods of our interface make sure that we use the getTransformationMethod to identify the name of a method that can transform data labeled by $field and then will call that method when we need it returning its result.