py-zope.contentprovider/zope.contentprovider-3.7.2/PKG-INFO

Metadata-Version: 1.0
Name: zope.contentprovider
Version: 3.7.2
Summary: Content Provider Framework for Zope Templates
Home-page: http://pypi.python.org/pypi/zope.contentprovider
Author: Zope Foundation and Contributors
Author-email: zope-dev@zope.org
License: ZPL 2.1
Description: =================
        Content Providers
        =================

        This package provides a framework to develop componentized Web GUI
        applications. Instead of describing the content of a page using a single
        template or static system of templates and METAL macros, content provider
        objects are dynamically looked up based on the setup/configuration of the
        application.

        .. contents::

        Motivation and Design Goals
        ---------------------------

        Before diving into the features of this package let me take up a few bytes of
        text to explain the use cases that drove us to develop this package (also
        others) and how the API documented below fulfills/solves those use cases. When
        we started developing Zope 3, it was from a desire to decentralize
        functionality and thus the complexity of the Python code. And we were
        successful! The component architecture is a marvelous piece of software that
        hopefully will allow us to build scalable solutions for a very long
        time. However, when it comes to user interface design, in this case
        specifically HTML pages, we have failed to provide the features and patterns
        of assembeling a page from configured components.

        Looking up views for a particular content component and a request just simply
        does not work by itself. The content inside the page is still monolithic. One
        attempt to solve this problem are METAL macros, which allow you to insert
        other TAL snippets into your main template. But macros have two shortcomings.
        For one there is a "hard-coded" one-to-one mapping between a slot and the
        macro that fills that slot, which makes it impossible to register several
        macros for a given location. The second problem is that macros are not views
        in their own right; thus they cannot provide functionality that is independent
        of the main template's view.

        A second approach to modular UI design are rendering pipes. Rendering pipes
        have the great advantage that they can reach all regions of the page during
        every step of the rendering process. For example, if we have a widget in the
        middle of the page that requires some additional Javascript, then it is easy
        for a rendering unit to insert the Javascript file link in the HTML header of
        the page. This type of use case is very hard to solve using page
        templates. However, pipes are not the answer to componentized user interface,
        since they cannot simply deal with registering random content for a given page
        region. In fact, I propose that pipelines are orthogonal to content providers,
        the concept introducted below. A pipeline framework could easily use
        functionality provided by this and other packages to provide component-driven
        UI design.

        So our goal is clear: Bring the pluggability of the component architecture
        into page templates and user interface design. Zope is commonly known to
        reinvent the wheel, develop its own terminology and misuse other's terms. For
        example, the Plone community has a very different understanding of what a
        "portlet" is compared to the commonly accepted meaning in the corporate world,
        which derives its definition from JSR 168. Therefore an additional use case of
        the design of this package was to stick with common terms and use them in
        their original meaning -- well, given a little extra twist.

        The most basic user interface component in the Web application Java world is
        the "content provider" [1]_. A content provider is simply responsible for
        providing HTML content for a page. This is equivalent to a view that does not
        provide a full page, but just a snippet, much like widgets or macros. Once
        there is a way to configure those content providers, we need a way to
        insert them into our page templates. In our implementation this is
        accomplished using a new TALES namespace that allows to insert content
        providers by name. But how, you might wonder, does this provide a
        componentized user interface? On the Zope 3 level, each content provider is
        registered as a presentation component discriminated by the context, request
        and view it will appear in. Thus different content providers will be picked
        for different configurations.

        Okay, that's pretty much everything there is to say about content
        providers. What, we are done? Hold on, what about defining regions of pages
        and filling them configured UI snippets. The short answer is: See the
        ``zope.viewlet`` pacakge. But let me also give you the long answer. This and
        the other pacakges were developed using real world use cases. While doing
        this, we noticed that not every project would need, for example, all the
        features of a portlet, but would still profit from lower-level features. Thus
        we decided to declare clear boundaries of functionality and providing each
        level in a different package. This particualr package is only meant to provide
        the interface between the content provider world and page templates.

        .. [1] Note that this is a bit different from the role named content provider,
               which refers to a service that provides content; the content provider
               we are talking about here are the software components the service would
               provide to an application.


        Content Providers
        -----------------

        Content Provider is a term from the Java world that refers to components that
        can provide HTML content. It means nothing more! How the content is found and
        returned is totally up to the implementation. The Zope 3 touch to the concept
        is that content providers are multi-adapters that are looked up by the
        context, request (and thus the layer/skin), and view they are displayed in.

        The second important concept of content providers are their two-phase
        rendering design. In the first phase the state of the content provider is
        prepared and, if applicable, any data the provider is responsible for is
        updated.

          >>> from zope.contentprovider import interfaces

        So let's create a simple content provider:

          >>> import zope.interface
          >>> import zope.component
          >>> from zope.publisher.interfaces import browser

          >>> class MessageBox(object):
          ...     zope.interface.implements(interfaces.IContentProvider)
          ...     zope.component.adapts(zope.interface.Interface,
          ...                           browser.IDefaultBrowserLayer,
          ...                           zope.interface.Interface)
          ...     message = u'My Message'
          ...
          ...     def __init__(self, context, request, view):
          ...         self.__parent__ = view
          ...
          ...     def update(self):
          ...         pass
          ...
          ...     def render(self):
          ...         return u'<div class="box">%s</div>' %self.message

        The ``update()`` method is executed during phase one. Since no state needs to
        be calculated and no data is modified by this simple content provider, it is
        an empty implementation. The ``render()`` method implements phase 2 of the
        process. We can now instantiate the content provider (manually) and render it:

          >>> box = MessageBox(None, None, None)
          >>> box.render()
          u'<div class="box">My Message</div>'

        Since our content provider did not require the context, request or view to
        create its HTML content, we were able to pass trivial dummy values into the
        constructor. Also note that the provider must have a parent (using the
        ``__parent__`` attribute) specified at all times. The parent must be the view
        the provider appears in.

        I agree, this functionally does not seem very useful now. The constructor and
        the ``update()`` method seem useless and the returned content is totally
        static. However, we implemented a contract for content providers that other
        code can rely on. Content providers are (commonly) instantiated using the
        context, request and view they appear in and are required to always generate
        its HTML using those three components.


        Two-Phased Content Providers
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

        Let's now have a look at a content provider that actively uses the two-phase
        rendering process. The simpler scenario is the case where the content provider
        updates a content component without affecting anything else. So let's create a
        content component to be updated,

          >>> class Article(object):
          ...     title = u'initial'
          >>> article = Article()

        and the content provider that is updating the title:

          >>> class ChangeTitle(object):
          ...     zope.interface.implements(interfaces.IContentProvider)
          ...     zope.component.adapts(zope.interface.Interface,
          ...                           browser.IDefaultBrowserLayer,
          ...                           zope.interface.Interface)
          ...     fieldName = 'ChangeTitle.title'
          ...
          ...     def __init__(self, context, request, view):
          ...         self.__parent__ = view
          ...         self.context, self.request = context, request
          ...
          ...     def update(self):
          ...         if self.fieldName in self.request:
          ...             self.context.title = self.request[self.fieldName]
          ...
          ...     def render(self):
          ...         return u'<input name="%s" value="%s" />' % (self.fieldName,
          ...                                                     self.context.title)

        Using a request, let's now instantiate the content provider and go through the
        two-phase rendering process:

          >>> from zope.publisher.browser import TestRequest
          >>> request = TestRequest()
          >>> changer = ChangeTitle(article, request, None)
          >>> changer.update()
          >>> changer.render()
          u'<input name="ChangeTitle.title" value="initial" />'

        Let's now enter a new title and render the provider:

          >>> request = TestRequest(form={'ChangeTitle.title': u'new title'})
          >>> changer = ChangeTitle(article, request, None)
          >>> changer.update()
          >>> changer.render()
          u'<input name="ChangeTitle.title" value="new title" />'
          >>> article.title
          u'new title'

        So this was easy. Let's now look at a case where one content provider's update
        influences the content of another. Let's say we have a content provider that
        displays the article's title:

          >>> class ViewTitle(object):
          ...     zope.interface.implements(interfaces.IContentProvider)
          ...     zope.component.adapts(zope.interface.Interface,
          ...                           browser.IDefaultBrowserLayer,
          ...                           zope.interface.Interface)
          ...
          ...     def __init__(self, context, request, view):
          ...         self.context, self.__parent__ = context, view
          ...
          ...     def update(self):
          ...         pass
          ...
          ...     def render(self):
          ...         return u'<h1>Title: %s</h1>' % self.context.title

        Let's now say that the `ShowTitle` content provider is shown on a page
        *before* the `ChangeTitle` content provider. If we do the full rendering
        process for each provider in sequence, we get the wrong result:

          >>> request = TestRequest(form={'ChangeTitle.title': u'newer title'})

          >>> viewer = ViewTitle(article, request, None)
          >>> viewer.update()
          >>> viewer.render()
          u'<h1>Title: new title</h1>'

          >>> changer = ChangeTitle(article, request, None)
          >>> changer.update()
          >>> changer.render()
          u'<input name="ChangeTitle.title" value="newer title" />'

        So the correct way of doing this is to first complete phase 1 (update) for all
        providers, before executing phase 2 (render):

          >>> request = TestRequest(form={'ChangeTitle.title': u'newest title'})

          >>> viewer = ViewTitle(article, request, None)
          >>> changer = ChangeTitle(article, request, None)

          >>> viewer.update()
          >>> changer.update()

          >>> viewer.render()
          u'<h1>Title: newest title</h1>'

          >>> changer.render()
          u'<input name="ChangeTitle.title" value="newest title" />'


        ``UpdateNotCalled`` Errors
        ~~~~~~~~~~~~~~~~~~~~~~~~~~

        Since calling ``update()`` before any other method that mutates the provider
        or any other data is so important to the correct functioning of the API, the
        developer has the choice to raise the ``UpdateNotCalled`` error, if any method
        is called before ``update()`` (with exception of the constructor):

          >>> class InfoBox(object):
          ...     zope.interface.implements(interfaces.IContentProvider)
          ...     zope.component.adapts(zope.interface.Interface,
          ...                           browser.IDefaultBrowserLayer,
          ...                           zope.interface.Interface)
          ...
          ...     def __init__(self, context, request, view):
          ...         self.__parent__ = view
          ...         self.__updated = False
          ...
          ...     def update(self):
          ...         self.__updated = True
          ...
          ...     def render(self):
          ...         if not self.__updated:
          ...             raise interfaces.UpdateNotCalled
          ...         return u'<div>Some information</div>'

          >>> info = InfoBox(None, None, None)

          >>> info.render()
          Traceback (most recent call last):
          ...
          UpdateNotCalled: ``update()`` was not called yet.

          >>> info.update()

          >>> info.render()
          u'<div>Some information</div>'


        The TALES ``provider`` Expression
        ---------------------------------

        The ``provider`` expression will look up the name of the content provider,
        call it and return the HTML content. The first step, however, will be to
        register our content provider with the component architecture:

          >>> zope.component.provideAdapter(MessageBox, name='mypage.MessageBox')

        The content provider must be registered by name, since the TALES expression
        uses the name to look up the provider at run time.

        Let's now create a view using a page template:

          >>> import os, tempfile
          >>> temp_dir = tempfile.mkdtemp()
          >>> templateFileName = os.path.join(temp_dir, 'template.pt')
          >>> open(templateFileName, 'w').write('''
          ... <html>
          ...   <body>
          ...     <h1>My Web Page</h1>
          ...     <div class="left-column">
          ...       <tal:block replace="structure provider:mypage.MessageBox" />
          ...     </div>
          ...     <div class="main">
          ...       Content here
          ...     </div>
          ...   </body>
          ... </html>
          ... ''')

        As you can see, we exprect the ``provider`` expression to simply look up the
        content provider and insert the HTML content at this place.

        Next we register the template as a view (browser page) for all objects:

          >>> from zope.browserpage.simpleviewclass import SimpleViewClass
          >>> FrontPage = SimpleViewClass(templateFileName, name='main.html')

          >>> zope.component.provideAdapter(
          ...     FrontPage,
          ...     (zope.interface.Interface, browser.IDefaultBrowserLayer),
          ...     zope.interface.Interface,
          ...     name='main.html')

        Let's create a content object that can be viewed:

          >>> class Content(object):
          ...     zope.interface.implements(zope.interface.Interface)

          >>> content = Content()

        Finally we look up the view and render it. Note that a
        BeforeUpdateEvent is fired - this event should always be fired before
        any contentprovider is updated.

          >>> from zope.publisher.browser import TestRequest
          >>> events = []
          >>> zope.component.provideHandler(events.append, (None, ))
          >>> request = TestRequest()

          >>> view = zope.component.getMultiAdapter((content, request),
          ...                                       name='main.html')
          >>> print view().strip()
          <html>
            <body>
              <h1>My Web Page</h1>
              <div class="left-column">
                <div class="box">My Message</div>
              </div>
              <div class="main">
                Content here
              </div>
            </body>
          </html>

          >>> events
          [<zope.contentprovider.interfaces.BeforeUpdateEvent object at ...>]

        The event holds the provider and the request.

          >>> events[0].request
          <zope.publisher.browser.TestRequest instance URL=http://127.0.0.1>
          >>> events[0].object
          <MessageBox object at ...>

        Failure to lookup a Content Provider
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

        If the name is not found, an error is raised. To demonstrate this behavior
        let's create another template:

          >>> errorFileName = os.path.join(temp_dir, 'error.pt')
          >>> open(errorFileName, 'w').write('''
          ... <html>
          ...   <body>
          ...     <tal:block replace="structure provider:mypage.UnknownName" />
          ...   </body>
          ... </html>
          ... ''')

          >>> ErrorPage = SimpleViewClass(errorFileName, name='error.html')
          >>> zope.component.provideAdapter(
          ...     ErrorPage,
          ...     (zope.interface.Interface, browser.IDefaultBrowserLayer),
          ...     zope.interface.Interface,
          ...     name='main.html')

          >>> errorview = zope.component.getMultiAdapter((content, request),
          ...                                            name='main.html')
          >>> print errorview()
          Traceback (most recent call last):
          ...
          ContentProviderLookupError: mypage.UnknownName


        Additional Data from TAL
        ~~~~~~~~~~~~~~~~~~~~~~~~

        The ``provider`` expression allows also for transferring data from the TAL
        context into the content provider. This is accomplished by having the content
        provider implement an interface that specifies the attributes and provides
        ``ITALNamespaceData``:

          >>> import zope.schema
          >>> class IMessageText(zope.interface.Interface):
          ...     message = zope.schema.Text(title=u'Text of the message box')

          >>> zope.interface.directlyProvides(IMessageText,
          ...                                 interfaces.ITALNamespaceData)

        Now the message box can receive its text from the TAL environment:

          >>> class DynamicMessageBox(MessageBox):
          ...     zope.interface.implements(IMessageText)

          >>> zope.component.provideAdapter(
          ...     DynamicMessageBox, provides=interfaces.IContentProvider,
          ...     name='mypage.DynamicMessageBox')

        We are now updating our original template to provide the message text:

          >>> open(templateFileName, 'w').write('''
          ... <html>
          ...   <body>
          ...     <h1>My Web Page</h1>
          ...     <div class="left-column">
          ...       <tal:block define="message string:Hello World!"
          ...                  replace="structure provider:mypage.DynamicMessageBox" />
          ...       <tal:block define="message string:Hello World again!"
          ...                  replace="structure provider:mypage.DynamicMessageBox" />
          ...     </div>
          ...     <div class="main">
          ...       Content here
          ...     </div>
          ...   </body>
          ... </html>
          ... ''')

        Now we should get two message boxes with different text:

          >>> print view().strip()
          <html>
            <body>
              <h1>My Web Page</h1>
              <div class="left-column">
                <div class="box">Hello World!</div>
                <div class="box">Hello World again!</div>
              </div>
              <div class="main">
                Content here
              </div>
            </body>
          </html>

        Finally, a content provider can also implement several ``ITALNamespaceData``:

          >>> class IMessageType(zope.interface.Interface):
          ...     type = zope.schema.TextLine(title=u'The type of the message box')

          >>> zope.interface.directlyProvides(IMessageType,
          ...                                 interfaces.ITALNamespaceData)

        We'll change our message box content provider implementation a bit, so the new
        information is used:

          >>> class BetterDynamicMessageBox(DynamicMessageBox):
          ...     zope.interface.implements(IMessageType)
          ...     type = None
          ...
          ...     def render(self):
          ...         return u'<div class="box,%s">%s</div>' %(self.type, self.message)

          >>> zope.component.provideAdapter(
          ...     BetterDynamicMessageBox, provides=interfaces.IContentProvider,
          ...     name='mypage.MessageBox')

        Of course, we also have to make our tempalte a little bit more dynamic as
        well:

          >>> open(templateFileName, 'w').write('''
          ... <html>
          ...   <body>
          ...     <h1>My Web Page</h1>
          ...     <div class="left-column">
          ...       <tal:block define="message string:Hello World!;
          ...                          type string:error"
          ...                  replace="structure provider:mypage.MessageBox" />
          ...       <tal:block define="message string:Hello World again!;
          ...                          type string:warning"
          ...                  replace="structure provider:mypage.MessageBox" />
          ...     </div>
          ...     <div class="main">
          ...       Content here
          ...     </div>
          ...   </body>
          ... </html>
          ... ''')

        Now we should get two message boxes with different text and types:

          >>> print view().strip()
          <html>
            <body>
              <h1>My Web Page</h1>
              <div class="left-column">
                <div class="box,error">Hello World!</div>
                <div class="box,warning">Hello World again!</div>
              </div>
              <div class="main">
                Content here
              </div>
            </body>
          </html>


        Base class
        ----------

        The ``zope.contentprovider.provider`` module provides an useful base
        class for implementing content providers. It has all boilerplate code
        and it's only required to override the ``render`` method to make it
        work:

          >>> from zope.contentprovider.provider import ContentProviderBase
          >>> class MyProvider(ContentProviderBase):
          ...     def render(self, *args, **kwargs):
          ...         return 'Hi there'

          >>> provider = MyProvider(None, None, None)
          >>> interfaces.IContentProvider.providedBy(provider)
          True

          >>> provider.update()
          >>> print provider.render()
          Hi there

        Note, that it can't be used as is, without providing the ``render`` method:

          >>> bad = ContentProviderBase(None, None, None)
          >>> bad.update()
          >>> print bad.render()
          Traceback (most recent call last):
          ...
          NotImplementedError: ``render`` method must be implemented by subclass

        You can add the update logic into the ``update`` method as with any content
        provider and you can implement more complex rendering patterns, based on
        templates, using this ContentProviderBase class as a base.


        You might also want to look at the ``zope.viewlet`` package for a more
        featureful API.

        Let's remove all temporary data we created during this README.

          >>> import shutil
          >>> shutil.rmtree(temp_dir)


        =======
        CHANGES
        =======

        3.7.2 (2010-05-25)
        ------------------

        - Fixed unit tests broken under Python 2.4 by the switch to the standard
          library ``doctest`` module.


        3.7.1 (2010-04-30)
        ------------------

        - Prefer the standard library's ``doctest`` module to the one from
          ``zope.testing.``


        3.7 (2010-04-27)
        ----------------

        - Since ``tales:expressiontype`` is now in ``zope.browserpage``, update
          conditional ZCML accordingly so it doesn't depend on the presence of
          ``zope.app.pagetemplate`` anymore.


        3.6.1 (2009-12-23)
        ------------------

        - Ensure that our ``configure.zcml`` can be loaded without requiring further
          dependencies. It uses a ``tales:expressiontype`` directive defined in
          ``zope.app.pagetemplate.`` We keep that dependency optional, as not all
          consumers of this package use ZCML to configure the expression type.


        3.6.0 (2009-12-22)
        ------------------

        - Updated test dependency to use ``zope.browserpage``.


        3.5.0 (2009-03-18)
        ------------------

        - Add very simple, but useful base class for implementing content
          providers, see ``zope.contentprovider.provider.ContentProviderBase``.

        - Remove unneeded testing dependencies. We only need ``zope.testing`` and
          ``zope.app.pagetemplate``.

        - Remove zcml slug and old zpkg-related files.

        - Added setuptools dependency to setup.py.

        - Clean up package's description and documentation a bit. Remove
          duplicate text in README.

        - Change mailing list address to zope-dev at zope.org instead of
          retired one.

        - Change ``cheeseshop`` to ``pypi`` in the package url.


        3.4.0 (2007-10-02)
        ------------------

        - Initial release independent of the main Zope tree.

Keywords: zope3 content provider
Platform: UNKNOWN
Classifier: Development Status :: 5 - Production/Stable
Classifier: Environment :: Web Environment
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Zope Public License
Classifier: Programming Language :: Python
Classifier: Natural Language :: English
Classifier: Operating System :: OS Independent
Classifier: Topic :: Internet :: WWW/HTTP
Classifier: Framework :: Zope3