Support value casting (closes #13)

[frostieDE]

Enables values casting

[magnusnordlander]

Thanks for this PR! This seems like a useful feature, I would however prefer for there to be an interface that enum classes can implement and checking for that instead of using method_exists.

[frostieDE]

In general, I agree with your proposal. But here is the thing: In case of convertToPHPValue I do not have an instance of the target enum class, thus I cannot check whether it implements any interface (at least not using instanceof). The only way to check whether the enum implements the needed interface, I have to use reflection.

So: do you thing it is worth implementing?

[frostieDE]

When thinking about it, I am not sure whether such functionality should be implemented in the enum itself. What I actually want to do with both methods is converting the value.

Maybe we can leverage a custom annotation and seperate converter classes:

interface EnumConverterInterface {

    /**
     * @param string $value
     * @return mixed
     */
    public function castValueIn($value);

    /**
     * @param mixed $value
     * @return string
     */
    public function castValueOut($value);
}

class IntegerEnumValuesConverter implements EnumConverterInterface {

    public function castValueIn($value) {
        return (int)$value;
    }

    public function castValueOut($value) {
        return (string)$value;
    }
}

use MyCLabs\Enum\Enum;

/**
 * @EnumConverter(converterClass="IntegerEnumValuesConverter")
 * @method static StudyGroupType Grade()
 * @method static StudyGroupType Course()
 */
class StudyGroupType extends Enum {
    private const Grade = 1;
    private const Course = 2;
}

The code would be a bit more complicated than before, but I guess it would be more flexible?

Downside of this approach: we cannot inject the AnnotationReader which is created by Symfony thus we cannot use any caching functionalities...