public function validate($value)
    {
        return class_exists($value) || interface_exists($value) ? Ok::unit() : Error::unit([ Error::CLASS_NOT_EXISTS ]);
    }
public function validate($value)
    {
        return class_exists($value) || interface_exists($value) ? Ok::unit() : Error::unit([ Error::CLASS_NOT_EXISTS ]);
    }
public function validate ( $ value ) { return class_exists ( $ value ) || interface_exists ( $ value ) ? Ok :: unit ( ) : Error :: unit ( [ Error :: CLASS_NOT_EXISTS ] ) ; }
Tells if a given value is a fully qualified class name of an existing php class.

@param mixed $value

@return ResultInterface Returns Ok if the value is valid, otherwise an Error is returned.
Tells if a given value is a fully qualified class name of an existing php class .