django-viewlet 1.5.1

Jinja2

If you’re using Jinja2 as your template engine for Django versions < 1.8, put this in your Django settings:

VIEWLET_TEMPLATE_ENGINE = 'jinja2'

If you’re using Coffin or Jingo, add the ViewletExtension to their settings, and optionally switch to their respective environment.

Coffin:

JINJA2_EXTENSIONS = (
    ...
    'viewlet.loaders.jinja2_loader.ViewletExtension',
)

VIEWLET_JINJA2_ENVIRONMENT = 'coffin.common.env'

Jingo:

JINJA_CONFIG = {
    'extensions': (
        ...
       'viewlet.loaders.jinja2_loader.ViewletExtension',
    ),
}

VIEWLET_JINJA2_ENVIRONMENT = 'jingo.get_env'

Django 1.8+:

Add ViewletExtension to the list of extensions of Jinja2 template engine

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.jinja2.Jinja2',
        # ...
        'OPTIONS': {
            # ...
            'extensions': [
                # ...
                'viewlet.loaders.jinja2_loader.ViewletExtension',
            ],
        }
    }
],

Specifying cache backend

By default viewlet will try using viewlet cache alias, falling back to default. You can specify which alias should be used in settings:

VIEWLET_DEFAULT_CACHE_ALIAS = 'template_cache'

CACHES = {
    # ...
    'template_cache': {
        # ...
    },
    # ...
}

Additionally, you can override cache alias in viewlet decorator with using argument

@viewlet(using='super_cache')
def hello_user(context, name):
    return render_to_string('hello_user.html', {'name': name})

Refreshing viewlets

A cached viewlet can be re-rendered and updated behind the scenes with viewlet.refresh

import viewlet
viewlet.refresh('hello_user', 'monkey')
# or
hello_user.refresh('monkey')

The decorator

@viewlet(name, template, key, timeout)

• name

  Optional reference name for the viewlet, defaults to function name.

• template

  Optional path to template. If specified the viewlet must return a context dict, otherwise it is responsible to return the rendered output itself.

• key

  Optional cache key, if not specified a dynamic key will be generated viewlet:name(args...)

• timeout

  Cache timeout. Defaults to configured cache backend default timeout, None = eternal, 0 = uncached.

Examples

The content returned by the viewlet will by default be cached. Use the timeout argument to change this.

@viewlet(timeout=30*60)
def hello_user(context, name):
    return render_to_string('hello_user.html', {'name': name})

Tip: Set timeout to None to cache forever and use viewlet.refresh to update the cache.

Django viewlet will by default build a cache key viewlet:name(args...). To customize this key pass a string to the viewlet decorator argument key that includes string mod operators for each viewlet argument.

@viewlet(timeout=30*60, key='some_cache_key_%s')
def hello_user(context, name):
    return render_to_string('hello_user.html', {'name': name})

Django viewlet will cache returned context instead of html by using the template decorator argument. This is useful if cached html is too heavy, or your viewlet template needs to be rendered on every call. The specified template will then be rendered with the viewlet context merged with the parent context, usually a RequestContext.

@viewlet(template='hello_user.html', timeout=30*60)
def hello_user(context, name):
    return {'name': name}

Note: Return context dict for the template, not rendered html/text

If there is no need for caching, set the viewlet decorator argument timeout to 0.

@viewlet(timeout=0)
def hello_user(context, name):
    return render_to_string('hello_user.html', {'name': name})

By default your viewlets will be named as the function. To override this you can set the decorator argument name

@viewlet(name='greeting')
def hello_user(context, name):
    return render_to_string('hello_user.html', {'name': name})

A powerful usage of viewlet.refresh is to use it together with Django signals:

class Product(Model):
    name = CharField(max_length=255)

@viewlet(timeout=None)
def product_teaser(context, id):
    product = get_context_object(Product, id, context)
    return render_to_string('product_teaser.html', locals())

def refresh_product_teaser(instance, **kwargs):
    viewlet.refresh('product_teaser', instance.id)

post_save.connect(refresh_product_teaser, Product)

Viewlets can also be accesses with AJAX by adding viewlet.urls to your Django root urls:

urlpatterns = patterns('',
    (r'^viewlet/', include('viewlet.urls')),
)

The url ends with the viewlet name followed by a querystring used as kwargs to the viewlet:

http://localhost:8000/viewlet/[name]/?arg=1…