silverstripe-framework/src/Forms/FormTransformation.php

<?php

namespace SilverStripe\Forms;

use BadMethodCallException;
use SilverStripe\Core\ClassInfo;
use SilverStripe\Core\Config\Configurable;
use SilverStripe\Core\Extensible;
use SilverStripe\Core\Injector\Injectable;

/**
 * This class represents "transformations" of a form - such as making it printable or making it readonly.
 * The idea is that sometimes you will want to make your own such transformations, and you shouldn't have
 * to edit the underlying code to support this.
 *
 * The first step in creating a transformation is subclassing FormTransformation.  After that, you have two
 * ways of defining specific functionality:
 *   - Define performMyTransformation() methods on each applicable FormField() object.
 *   - Define transformFieldType($field) methods on your subclass of FormTransformation.
 *
 * To actually perform the transformation, call $form->transform(new MyTransformation());
 */
class FormTransformation
{
    use Configurable;
    use Injectable;
    use Extensible;

    public function __construct()
    {
    }

    public function transform(FormField $field)
    {
        // Look for a performXXTransformation() method on the field itself.
        // performReadonlyTransformation() is a pretty commonly applied method.
        // Otherwise, look for a transformXXXField() method on this object.
        // This is more commonly done in custom transformations

        // We iterate through each array simultaneously, looking at [0] of both, then [1] of both.
        // This provides a more natural failover scheme.

        $transNames = array_reverse(array_map(
            function ($name) {
                return ClassInfo::shortName($name);
            },
            array_values(ClassInfo::ancestry($this) ?? [])
        ));
        $fieldClasses = array_reverse(array_map(
            function ($name) {
                return ClassInfo::shortName($name);
            },
            array_values(ClassInfo::ancestry($field) ?? [])
        ));

        $len = max(sizeof($transNames ?? []), sizeof($fieldClasses ?? []));
        for ($i=0; $i<$len; $i++) {
            // This is lets fieldClasses be longer than transNames
            if (!empty($transNames[$i])) {
                $funcName = 'perform' . $transNames[$i];
                if ($field->hasMethod($funcName)) {
                    //echo "<li>$field->class used $funcName";
                    return $field->$funcName($this);
                }
            }

            // And this one does the reverse.
            if (!empty($fieldClasses[$i])) {
                $funcName = 'transform' . $fieldClasses[$i];
                if ($this->hasMethod($funcName)) {
                    //echo "<li>$field->class used $funcName";
                    return $this->$funcName($field);
                }
            }
        }

        $class = static::class;
        $fieldClass = get_class($field);
        throw new BadMethodCallException("FormTransformation:: Can't perform '{$class}' on '{$fieldClass}'");
    }
}