python-zope.preference 3.8.0-0ubuntu4 / usr / share / pyshared / zope.preference-3.8.0.egg-info / PKG-INFO

Metadata-Version: 1.1
Name: zope.preference
Version: 3.8.0
Summary: User Preferences Framework
Home-page: http://pypi.python.org/pypi/zope.preference
Author: Zope Corporation and Contributors
Author-email: zope-dev@zope.org
License: ZPL 2.1
Description: This package provides and API to create and maintain hierarchical user
        preferences. Preferences can be easily created by defining schemas.
        
        
        .. contents::
        
        ================
        User Preferences
        ================
        
        Implementing user preferences is usually a painful task, since it requires a
        lot of custom coding and constantly changing preferences makes it hard to
        maintain the data and UI. The `preference` package
        
          >>> from zope.preference import preference
        
        eases this pain by providing a generic user preferences framework that uses
        schemas to categorize and describe the preferences.
        
        We also have to do some additional setup beforehand:
        
          >>> from zope.app.testing import setup
        
          >>> import zope.component.hooks
          >>> zope.component.hooks.setHooks()
          >>> setup.setUpTraversal()
          >>> setup.setUpSiteManagerLookup()
        
        
        Preference Groups
        ------------------
        
        Preferences are grouped in preference groups and the preferences inside a
        group are specified via the preferences group schema:
        
          >>> import zope.interface
          >>> import zope.schema
          >>> class IZMIUserSettings(zope.interface.Interface):
          ...     """Basic User Preferences"""
          ...
          ...     email = zope.schema.TextLine(
          ...         title=u"E-mail Address",
          ...         description=u"E-mail Address used to send notifications")
          ...
          ...     skin = zope.schema.Choice(
          ...         title=u"Skin",
          ...         description=u"The skin that should be used for the ZMI.",
          ...         values=['Rotterdam', 'ZopeTop', 'Basic'],
          ...         default='Rotterdam')
          ...
          ...     showZopeLogo = zope.schema.Bool(
          ...         title=u"Show Zope Logo",
          ...         description=u"Specifies whether Zope logo should be displayed "
          ...                     u"at the top of the screen.",
          ...         default=True)
        
        Now we can instantiate the preference group. Each preference group must have an
        ID by which it can be accessed and optional title and description fields for UI
        purposes:
        
          >>> settings = preference.PreferenceGroup(
          ...     "ZMISettings",
          ...     schema=IZMIUserSettings,
          ...     title=u"ZMI User Settings",
          ...     description=u"")
        
        Note that the preferences group provides the interface it is representing:
        
          >>> IZMIUserSettings.providedBy(settings)
          True
        
        and the id, schema and title of the group are directly available:
        
          >>> settings.__id__
          'ZMISettings'
          >>> settings.__schema__
          <InterfaceClass zope.preference.README.IZMIUserSettings>
          >>> settings.__title__
          u'ZMI User Settings'
        
        So let's ask the preference group for the `skin` setting:
        
          >>> settings.skin #doctest:+ELLIPSIS
          Traceback (most recent call last):
          ...
          NoInteraction
        
        
        So why did the lookup fail? Because we have not specified a principal yet, for
        which we want to lookup the preferences. To do that, we have to create a new
        interaction:
        
          >>> class Principal:
          ...     def __init__(self, id):
          ...         self.id = id
          >>> principal = Principal('zope.user')
        
          >>> class Participation:
          ...     interaction = None
          ...     def __init__(self, principal):
          ...         self.principal = principal
        
          >>> participation = Participation(principal)
        
          >>> import zope.security.management
          >>> zope.security.management.newInteraction(participation)
        
        We also need an IAnnotations adapter for principals, so we can store the
        settings:
        
          >>> from zope.annotation.interfaces import IAnnotations
          >>> class PrincipalAnnotations(dict):
          ...     zope.interface.implements(IAnnotations)
          ...     data = {}
          ...     def __new__(class_, principal, context):
          ...         try:
          ...             annotations = class_.data[principal.id]
          ...         except KeyError:
          ...             annotations = dict.__new__(class_)
          ...             class_.data[principal.id] = annotations
          ...         return annotations
          ...     def __init__(self, principal, context):
          ...         pass
        
          >>> from zope.component import provideAdapter
          >>> provideAdapter(PrincipalAnnotations,
          ...                (Principal, zope.interface.Interface), IAnnotations)
        
        Let's now try to access the settings again:
        
          >>> settings.skin
          'Rotterdam'
        
        which is the default value, since we have not set it yet. We can now reassign
        the value:
        
          >>> settings.skin = 'Basic'
          >>> settings.skin
          'Basic'
        
        However, you cannot just enter any value, since it is validated before the
        assignment:
        
          >>> settings.skin = 'MySkin'
          Traceback (most recent call last):
          ...
          ConstraintNotSatisfied: MySkin
        
        
        Preference Group Trees
        ----------------------
        
        The preferences would not be very powerful, if you could create a full
        preferences. So let's create a sub-group for our ZMI user settings, where we
        can adjust the look and feel of the folder contents view:
        
          >>> class IFolderSettings(zope.interface.Interface):
          ...     """Basic User Preferences"""
          ...
          ...     shownFields = zope.schema.Set(
          ...         title=u"Shown Fields",
          ...         description=u"Fields shown in the table.",
          ...         value_type=zope.schema.Choice(['name', 'size', 'creator']),
          ...         default=set(['name', 'size']))
          ...
          ...     sortedBy = zope.schema.Choice(
          ...         title=u"Sorted By",
          ...         description=u"Data field to sort by.",
          ...         values=['name', 'size', 'creator'],
          ...         default='name')
        
          >>> folderSettings = preference.PreferenceGroup(
          ...     "ZMISettings.Folder",
          ...     schema=IFolderSettings,
          ...     title=u"Folder Content View Settings")
        
        Note that the id was chosen so that the parent id is the prefix of the child's
        id. Our new preference sub-group should now be available as an attribute or an
        item on the parent group ...
        
          >>> settings.Folder
          Traceback (most recent call last):
          ...
          AttributeError: 'Folder' is not a preference or sub-group.
        
        ... but not before we register the groups as utilities:
        
          >>> from zope.preference import interfaces
          >>> from zope.component import provideUtility
        
          >>> provideUtility(settings, interfaces.IPreferenceGroup,
          ...                name='ZMISettings')
          >>> provideUtility(folderSettings, interfaces.IPreferenceGroup,
          ...                name='ZMISettings.Folder')
        
        If we now try to lookup the sub-group again, we should be successful:
        
          >>> settings.Folder #doctest:+ELLIPSIS
          <zope.preference.preference.PreferenceGroup object at ...>
        
          >>> settings['Folder'] #doctest:+ELLIPSIS
          <zope.preference.preference.PreferenceGroup object at ...>
        
        While the registry of the preference groups is flat, the careful naming of the
        ids allows us to have a tree of preferences. Note that this pattern is very
        similar to the way modules are handled in Python; they are stored in a flat
        dictionary in ``sys.modules``, but due to the naming they appear to be in a
        namespace tree.
        
        While we are at it, there are also preference categories that can be compared
        to Python packages. They basically are just a higher level grouping concept
        that is used by the UI to better organize the preferences. A preference group
        can be converted to a category by simply providing an additional interface:
        
          >>> zope.interface.alsoProvides(settings, interfaces.IPreferenceCategory)
        
          >>> interfaces.IPreferenceCategory.providedBy(settings)
          True
        
        
        Default Preferences
        -------------------
        
        It sometimes desirable to define default settings on a site-by-site basis,
        instead of just using the default value from the schema. The preferences
        package provides a module
        
          >>> from zope.preference import default
        
        that implements a default preferences provider that can be added as a unnamed
        utility for each site. So the first step is to create a site:
        
          >>> root = setup.buildSampleFolderTree()
          >>> rsm = setup.createSiteManager(root, True)
        
        Now we can register the default preference provider with the root site:
        
          >>> provider = setup.addUtility(rsm, '',
          ...                             interfaces.IDefaultPreferenceProvider,
          ...                             default.DefaultPreferenceProvider())
        
        So before we set an explicit default value for a preference, the schema field
        default is used:
        
          >>> settings.Folder.sortedBy
          'name'
        
        But if we now set a new default value with the provider,
        
          >>> defaultFolder = provider.getDefaultPreferenceGroup('ZMISettings.Folder')
          >>> defaultFolder.sortedBy = 'size'
        
        then the default of the setting changes:
        
          >>> settings.Folder.sortedBy
          'size'
        
        The default preference providers also implicitly acquire default values from
        parent sites. So if we make `folder1` a site and set it as the active site
        
          >>> folder1 = root['folder1']
          >>> sm1 = setup.createSiteManager(folder1, True)
        
        and add a default provider there,
        
          >>> provider1 = setup.addUtility(sm1, '',
          ...                              interfaces.IDefaultPreferenceProvider,
          ...                              default.DefaultPreferenceProvider())
        
        then we still get the root's default values, because we have not defined any
        in the higher default provider:
        
          >>> settings.Folder.sortedBy
          'size'
        
        But if we provide the new provider with a default value for `sortedBy`,
        
          >>> defaultFolder1 = provider1.getDefaultPreferenceGroup('ZMISettings.Folder')
          >>> defaultFolder1.sortedBy = 'creator'
        
        then it is used instead:
        
          >>> settings.Folder.sortedBy
          'creator'
        
        Of course, once the root site becomes our active site again
        
          >>> zope.component.hooks.setSite(root)
        
        the default value of the root provider is used:
        
          >>> settings.Folder.sortedBy
          'size'
        
        Of course, all the defaults in the world are not relevant anymore as soon as
        the user actually provides a value:
        
          >>> settings.Folder.sortedBy = 'name'
          >>> settings.Folder.sortedBy
          'name'
        
        Oh, and have I mentioned that entered values are always validated? So you
        cannot just assign any old value:
        
          >>> settings.Folder.sortedBy = 'foo'
          Traceback (most recent call last):
          ...
          ConstraintNotSatisfied: foo
        
        Finally, if the user deletes his/her explicit setting, we are back to the
        default value:
        
          >>> del settings.Folder.sortedBy
          >>> settings.Folder.sortedBy
          'size'
        
        
        Creating Preference Groups Using ZCML
        -------------------------------------
        
        If you are using the user preference system in Zope 3, you will not have to
        manually setup the preference groups as we did above (of course). We will use
        ZCML instead. First, we need to register the directives:
        
          >>> from zope.configuration import xmlconfig
          >>> import zope.preference
          >>> context = xmlconfig.file('meta.zcml', zope.preference)
        
        Then the system sets up a root preference group:
        
          >>> context = xmlconfig.string('''
          ...     <configure
          ...         xmlns="http://namespaces.zope.org/zope"
          ...         i18n_domain="test">
          ...
          ...       <preferenceGroup
          ...           id=""
          ...           title="User Preferences"
          ...           />
          ...
          ...     </configure>''', context)
        
        Now we can use the preference system in its intended way. We access the folder
        settings as follows:
        
          >>> import zope.component
          >>> prefs = zope.component.getUtility(interfaces.IPreferenceGroup)
          >>> prefs.ZMISettings.Folder.sortedBy
          'size'
        
        Let's register the ZMI settings again under a new name via ZCML:
        
          >>> context = xmlconfig.string('''
          ...     <configure
          ...         xmlns="http://namespaces.zope.org/zope"
          ...         i18n_domain="test">
          ...
          ...       <preferenceGroup
          ...           id="ZMISettings2"
          ...           title="ZMI Settings NG"
          ...           schema="zope.preference.README.IZMIUserSettings"
          ...           category="true"
          ...           />
          ...
          ...     </configure>''', context)
        
          >>> prefs.ZMISettings2 #doctest:+ELLIPSIS
          <zope.preference.preference.PreferenceGroup object at ...>
        
          >>> prefs.ZMISettings2.__title__
          u'ZMI Settings NG'
        
          >>> IZMIUserSettings.providedBy(prefs.ZMISettings2)
          True
          >>> interfaces.IPreferenceCategory.providedBy(prefs.ZMISettings2)
          True
        
        And the tree can built again by carefully constructing the id:
        
          >>> context = xmlconfig.string('''
          ...     <configure
          ...         xmlns="http://namespaces.zope.org/zope"
          ...         i18n_domain="test">
          ...
          ...       <preferenceGroup
          ...           id="ZMISettings2.Folder"
          ...           title="Folder Settings"
          ...           schema="zope.preference.README.IFolderSettings"
          ...           />
          ...
          ...     </configure>''', context)
        
          >>> prefs.ZMISettings2 #doctest:+ELLIPSIS
          <zope.preference.preference.PreferenceGroup object at ...>
        
          >>> prefs.ZMISettings2.Folder.__title__
          u'Folder Settings'
        
          >>> IFolderSettings.providedBy(prefs.ZMISettings2.Folder)
          True
          >>> interfaces.IPreferenceCategory.providedBy(prefs.ZMISettings2.Folder)
          False
        
        
        Simple Python-Level Access
        --------------------------
        
        If a site is set, getting the user preferences is very simple:
        
          >>> from zope.preference import UserPreferences
          >>> prefs2 = UserPreferences()
          >>> prefs2.ZMISettings.Folder.sortedBy
          'size'
        
        This function is also commonly registered as an adapter,
        
          >>> from zope.location.interfaces import ILocation
          >>> provideAdapter(UserPreferences, [ILocation], interfaces.IUserPreferences)
        
        so that you can adapt any location to the user preferences:
        
          >>> prefs3 = interfaces.IUserPreferences(folder1)
          >>> prefs3.ZMISettings.Folder.sortedBy
          'creator'
        
        
        Traversal
        ---------
        
        Okay, so all these objects are nice, but they do not make it any easier to
        access the preferences in page templates. Thus, a special traversal namespace
        has been created that makes it very simple to access the preferences via a
        traversal path. But before we can use the path expressions, we have to
        register all necessary traversal components and the special `preferences`
        namespace:
        
          >>> import zope.traversing.interfaces
          >>> provideAdapter(preference.preferencesNamespace, [None],
          ...                      zope.traversing.interfaces.ITraversable,
          ...                      'preferences')
        
        We can now access the preferences as follows:
        
          >>> from zope.traversing.api import traverse
          >>> traverse(None, '++preferences++ZMISettings/skin')
          'Basic'
          >>> traverse(None, '++preferences++/ZMISettings/skin')
          'Basic'
        
        
        Security
        --------
        
        You might already wonder under which permissions the preferences are
        available. They are actually available publicly (`CheckerPublic`), but that
        is not a problem, since the available values are looked up specifically for
        the current user. And why should a user not have full access to his/her
        preferences?
        
        Let's create a checker using the function that the security machinery is
        actually using:
        
          >>> checker = preference.PreferenceGroupChecker(settings)
          >>> checker.permission_id('skin')
          Global(CheckerPublic,zope.security.checker)
          >>> checker.setattr_permission_id('skin')
          Global(CheckerPublic,zope.security.checker)
        
        The id, title, description, and schema are publicly available for access,
        but are not available for mutation at all:
        
          >>> checker.permission_id('__id__')
          Global(CheckerPublic,zope.security.checker)
          >>> checker.setattr_permission_id('__id__') is None
          True
        
        
        The only way security could be compromised is when one could override the
        annotations property. However, this property is not available for public
        consumption at all, including read access:
        
          >>> checker.permission_id('annotation') is None
          True
          >>> checker.setattr_permission_id('annotation') is None
          True
        
        
        =======
        CHANGES
        =======
        
        3.8.0 (2010-06-12)
        ------------------
        
        - Split out from `zope.app.preference`.
        
        - Removed dependency on `zope.app.component.hooks` by using
          `zope.component.hooks`.
        
        - Removed dependency on `zope.app.container` by using
          `zope.container`.
Keywords: bluebream zope zope3 user preference
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