Returns application installation path.

        .. note::

            If fails this falls back to a restricted interface, which can only be used by approved apps.

        :rtype: str

def install_dir(self):
        """Returns application installation path.

        .. note::

            If fails this falls back to a restricted interface, which can only be used by approved apps.

        :rtype: str
        """
        max_len = 500

        directory = self._get_str(self._iface.get_install_dir, [self.app_id], max_len=max_len)

        if not directory:
            # Fallback to restricted interface (can only be used by approved apps).
            directory = self._get_str(self._iface_list.get_install_dir, [self.app_id], max_len=max_len)

        return directory