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View Rendering Decorator

Posted by Peter Ward on 2010-05-22 @ 06:03 and filed in Decorators

If you are planning on providing your views in multiple formats (e.g.: templated html, json, xml, whatever), you may like to return a dict from your views, and use a function to render the response. This snippet makes it easy to do that.

Usage:

from helpers import view, render_html, render_json

@view(app, '/<name>', render_html('page.html'))
@view(app, '/api/page/<name>', render_json)
def show_page(name):
    page = load_page(name)
    return dict(title=page.title, contents=page.contents)

The decorator to put in helpers.py is:

from myapp import app
from werkzeug import BaseResponse

def render_html(template, **defaults):
    def wrapped(result):
        variables = defaults.copy()
        variables.update(result)
        return render_template(template, **variables)
    return wrapped

def view(self, url, renderer=None, *args, **kwargs):
    super_route = self.route

    defaults = kwargs.pop('defaults', {})
    route_id = object()
    defaults['_route_id'] = route_id

    def deco(f):
        @super_route(url, defaults=defaults, *args, **kwargs)
        @wraps(f)
        def decorated_function(*args, **kwargs):
            this_route = kwargs.get('_route_id')
            if not getattr(f, 'is_route', False):
                del kwargs['_route_id']

            result = f(*args, **kwargs)

            if this_route is not route_id:
                return result

            # catch redirects.
            if isinstance(result, (app.response_class,
                                   BaseResponse)):
                return result

            if renderer is None:
                return result
            return renderer(result)

        decorated_function.is_route = True
        return decorated_function

    return deco

Other rendering functions (render_json, render_xml, etc.) are left as an exercise for the reader. ;)

This snippet by Peter Ward can be used freely for anything you like. Consider it public domain.