class GridView(BaseView):
    grid_cls = None
    template = 'grid-view.html'
    title = None

    def get(self):
        return self.render_grid()

    def render_grid(self):
        if self.grid_cls is None:
            raise NotImplementedError(
                'You must set {}.grid_cls to render a grid'.format(self.__class__.__name__)
            )

        g = self.grid_cls()
        g.apply_qs_args()

        if hasattr(self, 'setup_grid'):
            self.setup_grid(g)

        if g.export_to == 'xls':
            raise ImmediateResponse(g.xls.as_response())

        template_args = {
            'grid': g,
            'title': self.title,
        }

        return flask.render_template(
            self.template,
            **template_args
        )