rss
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Use Nagare namespaces to create an rss feed
In Nagare HTML and XML generation is done through Renderers. Thus, to generate RSS feeds it is possible to use Nagare XML Renderer, which accept any tag or attribute. Another way is to create a RSS Renderer for Nagare which matches RSS namespace.
To do so we are extending Nagare XmlRender, which enforces possible xml tags and attributes (e.g. namespace).
Simple RSSRenderer
RSS specification, leads to the following namespace definition in Nagare:
class RssRenderer(xml.XmlRenderer):
"""RSS renderer"""
# RSS tags
# ------------
rss = TagProp('rss', set(('version', )))
channel = TagProp('channel', set())
title = TagProp('title', set())
link = TagProp('link', set())
description = TagProp('description', set())
language = TagProp('language', set())
copyright = TagProp('copyright', set())
managingEditor = TagProp('managingEditor', set())
webMaster = TagProp('webMaster', set())
pubDate = TagProp('pubDate', set())
lastBuildDate = TagProp('lastBuildDate', set())
category = TagProp('category', set())
generator = TagProp('generator', set())
docs = TagProp('docs', set())
cloud = TagProp('cloud', set(('domain', 'port',
'path', 'registerProcedure', 'protocol')))
ttl = TagProp('ttl', set())
image = TagProp('image', set())
url = TagProp('url', set())
width = TagProp('width', set())
height = TagProp('height', set())
rating = TagProp('rating', set())
textInput = TagProp('textInput', set())
name = TagProp('name', set())
skipHours = TagProp('skipHours', set())
skipDays = TagProp('skipDays', set())
item = TagProp('item', set())
title = TagProp('title', set())
link = TagProp('link', set())
description = TagProp('description', set())
author = TagProp('author', set())
category = TagProp('category', set(('domain', )))
comments = TagProp('comments', set())
enclosure = TagProp('enclosure', set(('url', 'length', 'type')))
guid = TagProp('guid', set(('isPermaLink', )))
pubDate = TagProp('pubDate', set())
source = TagProp('source', set(('url', )))
Note
Notes:
- RssRenderer checks if tags and attibutes exist in namespace
- RssRenderer does not validate against any DTD or schema
Let's look at the following example:
<?xml version="1.0"?>
<rss version="2.0">
<channel>
<title>Some Blog Title</title>
<link>http://someblog.example.com</link>
<description>Description</description>
<language>en-us</language>
<pubDate>Tue, 25 Jan 2010 14:00:00 GMT</pubDate>
<lastBuildDate>Tue, 25 Jan 2010 14:00:00 GMT</lastBuildDate>
<docs>http://blogs.law.harvard.edu/tech/rss</docs>
<generator>Some Generator</generator>
<managingEditor>editor@example.com</managingEditor>
<webMaster>webmaster@example.com</webMaster>
<item>
<title>Some Post Title</title>
<link>http://someblog.example.com/post1</link>
<description>Some Post Description</description>
<pubDate>Tue, 25 Jan 2010 14:00:00 GMT</pubDate>
<guid>Some Global Unique Identifier</guid>
</item>
</channel>
</rss>
With RssRenderer, this feed is generated this way:
r = rss.RssRenderer()
with r.rss(version="2.0"):
with r.channel:
r << r.title('Some Blog Title')
r << r.link('http://someblog.example.com')
r << r.description('Description')
r << r.language('en-us')
r << r.pubDate('Tue, 25 Jan 2010 14:00:00 GMT')
r << r.lastBuildDate('Tue, 25 Jan 2010 14:00:00 GMT')
r << r.docs('http://blogs.law.harvard.edu/tech/rss')
r << r.generator('Some Generator')
r << r.managingEditor('editor@example.com')
r << r.webMaster('webmaster@example.com')
with r.item:
r << r.title('Some Post Title')
r << r.link('http://someblog.example.com/post1')
r << r.description('Some Post Description')
r << r.pubDate('Tue, 25 Jan 2010 14:00:00 GMT')
r << r.guid('Some Global Unique Identifier')
Now RSSRenderer can be used to generate any RSS feed.
Mixing multiple namespaces
There's several extensions to RSS, actually extensions are just XML namespaces added in the feed. One simple extension is blogChannel namespace.
First create a BlogChannelRenderer:
class BlogChannelRenderer(xml.XmlRenderer):
blogRoll = TagProp('blogRoll', set())
mySubscriptions = TagProp('mySubscriptions', set())
blink = TagProp('blink', set())
changes = TagProp('changes', set())
Now we can mix RssRenderer and BlogChannelRenderer to create one feed:
r = rss.RssRenderer()
r.namespaces = {'blogChannel': 'http://backend.userland.com/blogChannelModule'}
b = rss.BlogChannelRenderer(r)
b.default_namespace = 'blogChannel'
with r.rss(version="2.0"):
with r.channel:
r << r.title('Some Blog Title')
r << r.link('http://someblog.example.com')
r << r.description('Description')
r << r.language('en-us')
r << b.blogRoll('http://someblog.example.com/blogroll')
r << b.mySubscriptions('http://someblog.example.com/subscriptions')
r << b.blink('http://someblog.example.com/backlink')
r << b.changes('http://someblog.example.com/changes')
r << r.pubDate('Tue, 25 Jan 2010 14:00:00 GMT')
r << r.lastBuildDate('Tue, 25 Jan 2010 14:00:00 GMT')
r << r.docs('http://blogs.law.harvard.edu/tech/rss')
r << r.generator('Some Generator')
r << r.managingEditor('editor@example.com')
r << r.webMaster('webmaster@example.com')
with r.item:
r << r.title('Some Post Title')
r << r.link('http://someblog.example.com/post1')
r << r.description('Some Post Description')
r << r.pubDate('Tue, 25 Jan 2010 14:00:00 GMT')
r << r.guid('Some Global Unique Identifier')
This produces the following RSS feed:
<rss xmlns:blogChannel="http://backend.userland.com/blogChannelModule" version="2.0">
<channel>
<title>Some Blog Title</title>
<link>http://someblog.example.com</link>
<description>Description</description>
<language>en-us</language>
<blogChannel:blogRoll>http://someblog.example.com/blogroll</blogChannel:blogRoll>
<blogChannel:mySubscriptions>http://someblog.example.com/subscriptions</blogChannel:mySubscriptions>
<blogChannel:blink>http://someblog.example.com/backlink</blogChannel:blink>
<blogChannel:changes>http://someblog.example.com/changes</blogChannel:changes>
<pubDate>Tue, 25 Jan 2010 14:00:00 GMT</pubDate>
<lastBuildDate>Tue, 25 Jan 2010 14:00:00 GMT</lastBuildDate>
<docs>http://blogs.law.harvard.edu/tech/rss</docs>
<generator>Some Generator</generator>
<managingEditor>editor@example.com</managingEditor>
<webMaster>webmaster@example.com</webMaster>
<item>
<title>Some Post Title</title>
<link>http://someblog.example.com/post1</link>
<description>Some Post Description</description>
<pubDate>Tue, 25 Jan 2010 14:00:00 GMT</pubDate>
<guid>Some Global Unique Identifier</guid>
</item>
</channel>
</rss>
With this process any XML namespace can be added to Nagare. For example, Nagare XHTML namespace is implemented as a Renderer.
Common HTML structuration for different components
The problem
We want to obtain the same HTML structure when rendering different components.
Templating using inheritance and named views
The principle is the same than the template method design pattern but applied to components views.
Setting the base class
Let's declare an empty base class:
class BaseEntry(object):
pass
Its default view sets the common HTML structure and embeds the title and properties named views:
from nagare.presentation import render_for
@render_for(BaseEntry)
def render_BaseEntry(self, h, comp, *args):
"""All the views of entries will have this HTML structure"""
with h.div(class_='entry'):
with h.div(class_='title'):
h << comp.render(h, model='title')
with h.div(class_='properties'):
h << comp.render(h, model='properties')
return h.root
The BaseEntry's title and properties views are empty. They will be redefined for the derived classes:
@render_for(BaseEntry, model='title')
def render_BaseEntry_header(self, h, *args):
return h.root
@render_for(BaseEntry, model='properties')
def render_BaseEntry_header(self, h, *args):
return h.root
We can now verify that the basic HTML structure is generated:
>>> from nagare import component
>>> from nagare.namespaces import xhtml
>>>
>>> entry = component.Component(BaseEntry())
>>> h = xhtml.Renderer()
>>> print entry.render(h).write_htmlstring(pretty_print=True)
<div class="entry">
<div class="title"></div>
<div class="properties"></div>
</div>
Using the base class
Now, let's create a derived class:
class SimpleEntry(BaseEntry):
def __init__(self, name, firstname, age):
self.name = name
self.firstname = firstname
self.age = age
We only have to define its title and properties views:
@render_for(SimpleEntry, model='title')
def render_SimpleEntry_title(self, h, *args):
return '%s %s' % (self.firstname, self.name)
@render_for(SimpleEntry, model='properties')
def render_SimpleEntry_properties(self, h, *args):
return h.div('Age: %d' % self.age)
for the component data to be correctly inserted into the right HTML structure:
>>> from nagare import component
>>> from nagare.namespaces import xhtml
>>>
>>> entry = component.Component(SimpleEntry('John', 'Doe', 20))
>>> h = xhtml.Renderer()
>>> print entry.render(h).write_htmlstring(pretty_print=True)
<div class="entry">
<div class="title">Doe John</div>
<div class="properties"><div>Age: 20</div></div>
</div>
Templating using aggregation and named views
When inheritance is not wanted, we can define a component whose job is to do the rendering:
class EntryTemplate(object):
def __init__(self, entry):
self.entry = entry
@render_for(EntryTemplate)
def EntryTemplate(self, h, *args):
"""
Same code that we used in ``render_BaseEntry``
but using ``self.entry`` instead of ``self``.
"""
with h.div(class_='entry'):
with h.div(class_='title'):
h << self.entry.render(h, model='title')
with h.div(class_='properties'):
h << self.entry.render(h, model='properties')
return h.root
Let's use it with our SimpleEntry class:
class SimpleEntry(object): # no inheritance anymore
def __init__(self, name, firstname, age):
self.name = name
self.firstname = firstname
self.age = age
The title and properties views are still the same, but we must now declare a default view to wrap our SimpleEntry component into a EntryTemplate component and render it:
from nagare.component import Component
@render_for(SimpleEntry)
def render_SimpleEntry_header(self, h, comp, *args):
return Component(EntryTemplate(comp)).render(h)
Then we can use the SimpleEntry components exactly like in the previous chapter:
>>> from nagare import component
>>> from nagare.namespaces import xhtml
>>>
>>> entry = component.Component(SimpleEntry('John', 'Doe', 20))
>>> h = xhtml.Renderer()
>>> print entry.render(h).write_htmlstring(pretty_print=True)
<div class="entry">
<div class="title">Doe John</div>
<div class="properties"><div>Age: 20</div></div>
</div>