public function frontmatter($var = null)
    {

        if ($var) {
            $this->frontmatter = (string)$var;

            // Update also file object.
            $file = $this->file();
            if ($file) {
                $file->frontmatter((string)$var);
            }

            // Force content re-processing.
            $this->id(time() . md5($this->filePath()));
        }
        if (!$this->frontmatter) {
            $this->header();
        }

        return $this->frontmatter;
    }