Файл: pyramid.pdf

36.6. DEFINING VIEWS

5__name__ = None

6__parent__ = None

11

12def appmaker(zodb_root):

13if not ’app_root’ in zodb_root:

14app_root = Wiki()

15frontpage = Page(’This is the front page’)

16app_root[’FrontPage’] = frontpage

17frontpage.__name__ = ’FrontPage’

18frontpage.__parent__ = app_root

19zodb_root[’app_root’] = app_root

20import transaction

21transaction.commit()

22return zodb_root[’app_root’]

36.5.4 View the Application in a Browser

We can’t. At this point, our system is in a “non-runnable” state; we’ll need to change view-related files in the next chapter to be able to start the application successfully. If you try to start the application (See Start the Application), you’ll wind up with a Python traceback on your console that ends with this exception:

ImportError: cannot import name MyModel

This will also happen if you attempt to run the tests.

36.6 Defining Views

A view callable in a traversal -based Pyramid application is typically a simple Python function that accepts two parameters: context and request. A view callable is assumed to return a response object.

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latex-note.png

A Pyramid view can also be defined as callable which accepts only a request argument. You’ll see this one-argument pattern used in other Pyramid tutorials and applications. Either calling convention will work in any Pyramid application; the calling conventions can be used interchangeably as necessary. In traversal based applications, URLs are mapped to a context resource, and since our resource tree also represents our application’s “domain model”, we’re often interested in the context, because it represents the persistent storage of our application. For this reason, in this tutorial we define views as callables that accept context in the callable argument list. If you do need the context within a view function that only takes the request as a single argument, you can obtain it via request.context.

We’re going to define several view callable functions, then wire them into Pyramid using some view configuration.

The source code for this tutorial stage can be browsed via http://github.com/Pylons/pyramid/tree/1.3- branch/docs/tutorials/wiki/src/views/.

36.6.1 Declaring Dependencies in Our setup.py File

The view code in our application will depend on a package which is not a dependency of the original “tutorial” application. The original “tutorial” application was generated by the pcreate command; it doesn’t know about our custom application requirements. We need to add a dependency on the docutils package to our tutorial package’s setup.py file by assigning this dependency to the install_requires parameter in the setup function.

Our resulting setup.py should look like so:

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36.6. DEFINING VIEWS

11’pyramid_zodbconn’,

12’pyramid_tm’,

13’pyramid_debugtoolbar’,

14’ZODB3’,

15’waitress’,

16’docutils’,

17]

18

19setup(name=’tutorial’,

20version=’0.0’,

21description=’tutorial’,

22long_description=README + ’\n\n’ + CHANGES,

23classifiers=[

24"Intended Audience :: Developers",

25"Framework :: Pylons",

26"Programming Language :: Python",

27"Topic :: Internet :: WWW/HTTP",

28"Topic :: Internet :: WWW/HTTP :: WSGI :: Application",

29],

30author=’’,

31author_email=’’,

32url=’’,

33keywords=’web pylons pyramid’,

34packages=find_packages(),

35include_package_data=True,

36zip_safe=False,

37install_requires=requires,

38tests_require=requires,

39test_suite="tutorial",

40entry_points = """\

41[paste.app_factory]

42main = tutorial:main

43""",

44)

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After these new dependencies are added, you will need to rerun python setup.py develop inside the root of the tutorial package to obtain and register the newly added dependency package.

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36.6.2 Adding View Functions

We’re going to add four view callable functions to our views.py module. One view named view_wiki will display the wiki itself (it will answer on the root URL), another named view_page will display an individual page, another named add_page will allow a page to be added, and a final view named edit_page will allow a page to be edited.

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There is nothing special about the filename views.py. A project may have many view callables throughout its codebase in arbitrarily-named files. Files implementing view callables often have view in their filenames (or may live in a Python subpackage of your application package named views), but this is only by convention.

The view_wiki view function

The view_wiki function will be configured to respond as the default view callable for a Wiki resource. We’ll provide it with a @view_config decorator which names the class tutorial.models.Wiki as its context. This means that when a Wiki resource is the context, and no view name exists in the request, this view will be used. The view configuration associated with view_wiki does not use a renderer because the view callable always returns a response object rather than a dictionary. No renderer is necessary when a view returns a response object.

pyramid.httpexceptions.HTTPFound class (instances of which implement the pyramid.interfaces.IResponse interface like pyramid.response.Response does). The pyramid.request.Request.resource_url() API. pyramid.request.Request.resource_url() constructs a URL to the FrontPage page resource (e.g. http://localhost:6543/FrontPage), and uses it as the “location” of the HTTPFound response, forming an HTTP redirect.

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The view_page view function

The view_page function will be configured to respond as the default view of a Page resource. We’ll provide it with a @view_config decorator which names the class tutorial.models.Page as its context. This means that when a Page resource is the context, and no view name exists in the request, this view will be used. We inform Pyramid this view will use the templates/view.pt template file as a renderer.

The view_page function generates the ReStructuredText body of a page (stored as the data attribute of the context passed to the view; the context will be a Page resource) as HTML. Then it substitutes an HTML anchor for each WikiWord reference in the rendered HTML using a compiled regular expression.

The curried function named check is used as the first argument to wikiwords.sub, indicating that it should be called to provide a value for each WikiWord match found in the content. If the wiki (our page’s __parent__) already contains a page with the matched WikiWord name, the check function generates a view link to be used as the substitution value and returns it. If the wiki does not already contain a page with with the matched WikiWord name, the function generates an “add” link as the substitution value and returns it.

As a result, the content variable is now a fully formed bit of HTML containing various view and add links for WikiWords based on the content of our current page resource.

We then generate an edit URL (because it’s easier to do here than in the template), and we wrap up a number of arguments in a dictionary and return it.

The arguments we wrap into a dictionary include page, content, and edit_url. As a result, the template associated with this view callable (via renderer= in its configuration) will be able to use these names to perform various rendering tasks. The template associated with this view callable will be a template which lives in templates/view.pt.

Note the contrast between this view callable and the view_wiki view callable. In the view_wiki view callable, we unconditionally return a response object. In the view_page view callable, we return a dictionary. It is always fine to return a response object from a Pyramid view. Returning a dictionary is allowed only when there is a renderer associated with the view callable in the view configuration.

The add_page view function

The add_page function will be configured to respond when the context resource is a Wiki and the view name is add_page. We’ll provide it with a @view_config decorator which names the string add_page as its view name (via name=), the class tutorial.models.Wiki as its context, and the renderer named templates/edit.pt. This means that when a Wiki resource is the context, and a view name named add_page exists as the result of traversal, this view will be used. We inform Pyramid

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