Файл: pyramid.pdf

37.6. DEFINING VIEWS

Starting 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.

37.6 Defining Views

A view callable in a Pyramid application is typically a simple Python function that accepts a single parameter named request. A view callable is assumed to return a response object.

The request object passed to every view that is called as the result of a route match has an attribute named matchdict that contains the elements placed into the URL by the pattern of a route statement. For instance, if a call to pyramid.config.Configurator.add_route() in __init__.py had the pattern {one}/{two}, and the URL at http://example.com/foo/bar was invoked, matching this pattern, the matchdict dictionary attached to the request passed to the view would have a ’one’ key with the value ’foo’ and a ’two’ key with the value ’bar’.

The source code for this tutorial stage can be browsed at http://github.com/Pylons/pyramid/tree/1.3- branch/docs/tutorials/wiki2/src/views/.

37.6.1 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 requires parameter in setup().

Open tutorial/setup.py and edit it to look like the following:

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37. SQLALCHEMY + URL DISPATCH WIKI TUTORIAL

10’pyramid’,

11’SQLAlchemy’,

12’transaction’,

13’pyramid_tm’,

14’pyramid_debugtoolbar’,

15’zope.sqlalchemy’,

16’waitress’,

17’docutils’,

18]

19

20setup(name=’tutorial’,

21version=’0.0’,

22description=’tutorial’,

23long_description=README + ’\n\n’ + CHANGES,

24classifiers=[

25"Programming Language :: Python",

26"Framework :: Pylons",

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

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

29],

30author=’’,

31author_email=’’,

32url=’’,

33keywords=’web wsgi bfg pylons pyramid’,

34packages=find_packages(),

35include_package_data=True,

36zip_safe=False,

37test_suite=’tutorial’,

38install_requires = requires,

39entry_points = """\

40[paste.app_factory]

41main = tutorial:main

42[console_scripts]

43initialize_tutorial_db = tutorial.scripts.initializedb:main

44""",

45)

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37.6. DEFINING VIEWS

(Only the highlighted line needs to be added.)

37.6.2 Running setup.py develop

Since a new software dependency was 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 distribution.

Make sure your current working directory is the root of the project (the directory in which setup.py lives) and execute the following command.

On UNIX:

$ cd tutorial

$ ../bin/python setup.py develop

On Windows:

c:\pyramidtut> cd tutorial

c:\pyramidtut\tutorial> ..\Scripts\python setup.py develop

Success executing this command will end with a line to the console something like:

Finished processing dependencies for tutorial==0.0

37.6.3 Changing the views.py File

It’s time for a major change. Open tutorial/tutorial/views.py and edit it to look like the following:

9

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37. SQLALCHEMY + URL DISPATCH WIKI TUTORIAL

10from .models import (

11DBSession,

12Page,

13)

14

15# regular expression used to find WikiWords

16wikiwords = re.compile(r"\b([A-Z]\w+[A-Z]+\w+)")

17

18@view_config(route_name=’view_wiki’)

19def view_wiki(request):

20return HTTPFound(location = request.route_url(’view_page’,

22

23@view_config(route_name=’view_page’, renderer=’templates/view.pt’)

24def view_page(request):

25pagename = request.matchdict[’pagename’]

26page = DBSession.query(Page).filter_by(name=pagename).first()

27if page is None:

28return HTTPNotFound(’No such page’)

29

30def check(match):

31word = match.group(1)

32exists = DBSession.query(Page).filter_by(name=word).all()

33if exists:

35return ’<a href="%s">%s</a>’ % (view_url, word)

36else:

39

40content = publish_parts(page.data, writer_name=’html’)[’html_body’]

41content = wikiwords.sub(check, content)

42edit_url = request.route_url(’edit_page’, pagename=pagename)

43return dict(page=page, content=content, edit_url=edit_url)

44

45@view_config(route_name=’add_page’, renderer=’templates/edit.pt’)

46def add_page(request):

47name = request.matchdict[’pagename’]

48if ’form.submitted’ in request.params:

49body = request.params[’body’]

50page = Page(name, body)

51DBSession.add(page)

52return HTTPFound(location = request.route_url(’view_page’,

54save_url = request.route_url(’add_page’, pagename=name)

55page = Page(’’, ’’)

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37.6. DEFINING VIEWS

56 return dict(page=page, save_url=save_url)

57

58@view_config(route_name=’edit_page’, renderer=’templates/edit.pt’)

59def edit_page(request):

60name = request.matchdict[’pagename’]

61page = DBSession.query(Page).filter_by(name=name).one()

62if ’form.submitted’ in request.params:

63page.data = request.params[’body’]

64DBSession.add(page)

65return HTTPFound(location = request.route_url(’view_page’,

67return dict(

68page=page,

69save_url = request.route_url(’edit_page’, pagename=name),

70)

(The highlighted lines are the ones that need to be added or edited.)

We got rid of the my_view view function and its decorator that was added when we originally rendered the alchemy scaffold. It was only an example and isn’t relevant to our application.

Then we added four view callable functions to our views.py module:

•view_wiki() - Displays the wiki itself. It will answer on the root URL.

•view_page() - Displays an individual page.

•add_page() - Allows the user to add a page.

•edit_page() - Allows the user to edit a page.

We’ll describe each one briefly and show the resulting views.py file afterward.

latex-note.png

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.

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37. SQLALCHEMY + URL DISPATCH WIKI TUTORIAL

The view_wiki view function

view_wiki() is the default view that gets called when a request is made to the root URL of our wiki. It always redirects to a URL which represents the path to our “FrontPage”.

1 @view_config(route_name=’view_wiki’) 2 def view_wiki(request):

3return HTTPFound(location = request.route_url(’view_page’,

view_wiki() returns an instance of the pyramid.httpexceptions.HTTPFound class (instances of which implement the pyramid.interfaces.IResponse interface like pyramid.response.Response does).

It uses the pyramid.request.Request.route_url() API to construct a URL to the FrontPage page (e.g. http://localhost:6543/FrontPage), which is used as the “location” of the HTTPFound response, forming an HTTP redirect.

The view_page view function

view_page() is used to display a single page of our wiki. It renders the ReStructuredText body of a page (stored as the data attribute of a Page object) as HTML. Then it substitutes an HTML anchor for each WikiWord reference in the rendered HTML using a compiled regular expression.

1 @view_config(route_name=’view_page’, renderer=’templates/view.pt’) 2 def view_page(request):

3pagename = request.matchdict[’pagename’]

4 page = DBSession.query(Page).filter_by(name=pagename).first()

5if page is None:

6return HTTPNotFound(’No such page’)

7

8def check(match):

9word = match.group(1)

10exists = DBSession.query(Page).filter_by(name=word).all()

11if exists:

13return ’<a href="%s">%s</a>’ % (view_url, word)

14else:

464