unyx / notify

     * @return  $this

     * @throws  \InvalidArgumentException                       When $attachment is neither of the supported types.

     */

    public function attach($attachment) : Message

    {

        // Let's try to resolve the input into something usable.

        if (!($attachment = $this->resolveAttachment($attachment)) instanceof message\Attachment) {

            throw new \InvalidArgumentException("Expected a callable, an array or an instance of ".message\Attachment::class.", got [".diagnostics\Debug::getTypeName($attachment)."] instead.");

        }

        $this->attachments[] = $attachment;

        return $this;

    }

    /**

     * Checks whether an Attachment with the specified $index is set.

     * @return  $this

     * @throws  \InvalidArgumentException

     */

    public function setAttachment(int $index, $attachment) : Message

    {

        // Let's try to resolve the input into something usable.

        if (!($attachment = $this->resolveAttachment($attachment)) instanceof message\Attachment) {

            throw new \InvalidArgumentException("Expected a callable, an array or an instance of ".message\Attachment::class.", got [".diagnostics\Debug::getTypeName($attachment)."] instead.");

        }

        $this->attachments[$index] = $attachment;

        return $this;

    }

    /**

     * Returns the Attachments of the Message.