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diff --git a/docs/overview.txt b/docs/overview.txt new file mode 100644 index 0000000..61cb086 --- /dev/null +++ b/docs/overview.txt @@ -0,0 +1,596 @@ +============== +Django Tagging +============== + +A generic tagging application for `Django`_ projects, which allows +association of a number of tags with any ``Model`` instance and makes +retrieval of tags simple. + +.. _`Django`: http://www.djangoproject.com + + +Installation +============ + +Downloading django-tagging +-------------------------- + +There are two options for downloading; one is to download the latest +packaged version from http://code.google.com/p/django-tagging/ and +unpack it; inside is a script called setup.py. Type this command:: + + python setup.py install + +...and the package will install automatically. + +The other method is to perform a Subversion checkout from somewhere on +your Python path: + + svn checkout http://django-tagging.googlecode.com/svn/trunk/tagging/ + +Keep in mind that the current code in SVN may be different from the +packaged release, and may contain bugs and backwards-incompatible +changes. + +Using django-tagging in your projects +------------------------------------- + +Once you've downloaded django-tagging and want to use it in your +projects, do the following:: + + 1. Put ``'tagging'`` in your ``INSTALLED_APPS`` setting. + 2. Run the command ``manage.py syncdb``. + +The ``syncdb`` command creates the necessary database tables and +creates permission objects for all installed apps that need them. + +That's it! + + +Settings +======== + +Some of django-tagging's behaviour may be configured by adding the +appropriate settings to your project's settings file. + +The following settings are available: + +FORCE_LOWERCASE_TAGS +-------------------- + +Default: ``False`` + +A boolean that turns on/off forcing of tags to lowercase before they +are saved to the database. + + +Tags +==== + +Tags are represented by the ``Tag`` model, which lives in the +``tagging.models`` module. + +API reference +------------- + +Fields +~~~~~~ + +``Tag`` objects have the following fields: + + * ``name`` -- The name of the tag. This is a unique value + consisting only of unicode alphanumeric characters, numbers, + underscores and hyphens. + +Manager functions +~~~~~~~~~~~~~~~~~ + +The ``Tag`` model has a custom manager which has the following helper +functions: + + * ``update_tags(obj, tag_names)`` -- Updates tags associated with + an object. + + ``tag_names`` is a string containing tag names with which + ``obj`` should be tagged. Valid tag names may contain unicode + alphanumeric characters, numbers, underscores or hyphens. + Multiple tag names may be specified, separated by any number of + commas and spaces. + + If ``tag_names`` is ``None`` or ``''``, the object's tags will + be cleared. + + * ``add_tag(obj, tag_name)`` -- Associates a tag with an an object. + + ``tag_name`` is a string containing a tag name with which + ``obj`` should be tagged. Valid tag names may contain unicode + alphanumeric characters, numbers, underscores or hyphens. + + * ``get_for_object(obj)`` -- Returns a ``QuerySet`` containing all + ``Tag`` objects associated with ``obj``. + + * ``usage_for_model(Model, counts=False, min_count=None, filters=None)`` + -- Returns a list of ``Tag`` objects associated with instances + of ``Model``. + + If ``counts`` is ``True``, a ``count`` attribute will be added + to each tag, indicating how many times it has been associated + with instances of ``Model``. + + If ``min_count`` is given, only tags which have a ``count`` + greater than or equal to ``min_count`` will be returned. Passing + a value for ``min_count`` implies ``counts=True``. + + To limit the tags (and counts, if specified) returned to those + used by a subset of the model's instances, pass a dictionary of + field lookups to be applied to ``Model`` as the ``filters`` + argument. + + * ``related_for_model(tags, Model, counts=False, min_count=None)`` + -- Returns a list of tags related to a given list of tags - that + is, other tags used by items which have all the given tags. + + If ``counts`` is ``True``, a ``count`` attribute will be added + to each tag, indicating the number of items which have it in + addition to the given list of tags. + + If ``min_count`` is given, only tags which have a ``count`` + greater than or equal to ``min_count`` will be returned. Passing + a value for ``min_count`` implies ``counts=True``. + + * ``cloud_for_model(Model, steps=4, distribution=LOGARITHMIC, + filters=None, min_count=None)`` -- Returns a list of the + distinct ``Tag`` objects associated with instances of ``Model``, + each having a ``count`` attribute as above and an additional + ``font_size`` attribute, for use in creation of a tag cloud (a + type of weighted list). + + ``steps`` defines the number of font sizes available - + ``font_size`` may be an integer between ``1`` and ``steps``, + inclusive. + + ``distribution`` defines the type of font size distribution + algorithm which will be used - logarithmic or linear. It must + be either ``tagging.utils.LOGARITHMIC`` or + ``tagging.utils.LINEAR``. + + To limit the tags displayed in the cloud to those associated + with a subset of the Model's instances, pass a dictionary of + field lookups to be applied to the given Model as the + ``filters`` argument. + + To limit the tags displayed in the cloud to those with a + ``count`` greater than or equal to ``min_count``, pass a value + for the ``min_count`` argument. + +Basic usage +----------- + +Tagging objects and retrieving an object's tags +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Objects may be tagged using the ``update_tags`` helper function:: + + >>> from shop.apps.products.models import Widget + >>> from tagging.models import Tag + >>> widget = Widget.objects.get(pk=1) + >>> Tag.objects.update_tags(widget, 'house thing') + +Retrieve tags for an object using the ``get_for_object`` helper +function:: + + >>> Tag.objects.get_for_object(widget) + [<Tag: house>, <Tag: thing>] + +Tags are created, associated and unassociated accordingly when you use +``update_tags`` and ``add_tags``:: + + >>> Tag.objects.update_tags(widget, 'house monkey') + >>> Tag.objects.get_for_object(widget) + [<Tag: house>, <Tag: monkey>] + >>> Tag.objects.add_tag(widget, 'tiles') + >>> Tag.objects.get_for_object(widget) + [<Tag: house>, <Tag: monkey>, <Tag: tiles>] + +Clear an object's tags by passing ``None`` or ``''`` to +``update_tags``:: + + >>> Tag.objects.update_tags(widget, None) + >>> Tag.objects.get_for_object(widget) + [] + +Retrieving tags used by a particular model +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To retrieve all tags used for a particular model, use the +``get_for_model`` helper function:: + + >>> widget1 = Widget.objects.get(pk=1) + >>> Tag.objects.update_tags(widget1, 'house thing') + >>> widget2 = Widget.objects.get(pk=2) + >>> Tag.objects.update_tags(widget2, 'cheese toast house') + >>> Tag.objects.usage_for_model(Widget) + [<Tag: cheese>, <Tag: house>, <Tag: thing>, <Tag: toast>] + +To get a count of how many times each tag was used for a particular +model, pass in ``True`` for the ``counts`` argument:: + + >>> tags = Tag.objects.usage_for_model(Widget, counts=True) + >>> [(tag.name, tag.count) for tag in tags] + [('cheese', 1), ('house', 2), ('thing', 1), ('toast', 1)] + +To get counts and limit the tags returned to those with counts above a +certain size, pass in a ``min_count`` argument:: + + >>> tags = Tag.objects.usage_for_model(Widget, min_count=2) + >>> [(tag.name, tag.count) for tag in tags] + [('house', 2)] + +You can also specify a dictionary of `field lookups`_ to be used to +restrict the tags and counts returned based on a subset of the +model's instances. For example, the following would retrieve all tags +used on Widgets created by a user named Alan which have a size +greater than 99:: + + >>> Tag.objects.usage_for_model(Widget, filters=dict(size__gt=99, user__username='Alan')) + +.. _`field lookups`: http://www.djangoproject.com/documentation/db-api/#field-lookups + + +Tagged Items +============ + +The relationship between a ``Tag`` and an object is represented by +the ``TaggedItem`` model, which lives in the ``tagging.models`` +module. + +API reference +------------- + +Fields +~~~~~~ + +``TaggedItem`` objects have the following fields: + + * ``tag`` -- The ``Tag`` an object is associated with. + * ``content_type`` -- The ContentType of the associated object. + * ``object_id`` -- The id of the associated object. + * ``object`` -- The associated object. + +Manager functions +~~~~~~~~~~~~~~~~~ + +The ``TaggedItem`` model has a custom manager which has the following +helper functions: + + * ``get_by_model(Model, tag)`` -- If ``tag`` is an instance of a + ``Tag``, returns a ``QuerySet`` containing all instances of + ``Model`` which are tagged with it. + + If ``tag`` is a list of tags, returns a ``QuerySet`` containing + all instances of ``Model`` which are tagged with every tag in + the list. + + * ``get_intersection_by_model(Model, tags)`` -- Returns a + ``QuerySet`` containing all instances of ``Model`` which are + tagged with every tag in the list. + + ``get_by_model`` will call this function behind the scenes when + you pass it a list, so it's recommended that you use + ``get_by_model`` instead of calling this function directly. + + * ``get_related(obj, Model, num=None)`` - Returns instances of + ``Model`` which share tags with the model instance ``obj``, + ordered by the number of shared tags in descending order. + + If ``num`` is given, a maximum of ``num`` instances will be + returned. + +Basic usage +----------- + +Retrieving tagged objects +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Objects may be retrieved based on their tags using the ``get_by_model`` +helper function:: + + >>> from shop.apps.products.models import Widget + >>> from tagging.models import Tag + >>> house_tag = Tag.objects.get(name='house') + >>> TaggedItem.objects.get_by_model(Widget, house_tag) + [<Widget: pk=1>, <Widget: pk=2>] + +Passing a list of tags to ``get_by_model`` returns an intersection of +objects which have those tags, i.e. tag1 AND tag2 ... AND tagN:: + + >>> thing_tag = Tag.objects.get(name='thing') + >>> TaggedItem.objects.get_by_model(Widget, [house_tag, thing_tag]) + [<Widget: pk=1>] + +Functions which take tags are flexible when it comes to tag input:: + + >>> TaggedItem.objects.get_by_model(Widget, Tag.objects.filter(name__in=['house', 'thing'])) + [<Widget: pk=1>] + >>> TaggedItem.objects.get_by_model(Widget, 'house thing') + [<Widget: pk=1>] + >>> TaggedItem.objects.get_by_model(Widget, ['house', 'thing']) + [<Widget: pk=1>] + + +Utilities +========= + +Tag-related utility functions are defined in the ``tagging.utils`` +module: + +get_tag_name_list(tags_names) +----------------------------- + +Finds tag names in the given string and return them in a list. + +get_tag_list(tags) +------------------ + +Utility function for accepting tag input in a flexible manner. + +If a ``Tag`` object is given, it will be returned in a list as its +single occupant. + +If given, the tag names in the following will be used to create a +``Tag`` ``QuerySet``: + + * A string, which may contain multiple tag names. + * A list or tuple of strings corresponding to tag names. + * A list or tuple of integers corresponding to tag ids. + +If given, the following will be returned as-is: + + * A list or tuple of ``Tag`` objects. + * A ``Tag`` ``QuerySet``. + +calculate_cloud(tags, steps=4, distribution=tagging.utils.LOGARITHMIC) +---------------------------------------------------------------------- + +Adds a ``font_size`` attribute to each tag given according to the +frequency of its use, as indicated by its ``count`` attribute. + +``steps`` defines the range of font sizes - ``font_size`` will be an +integer between 1 and ``steps`` (inclusive). + +``distribution`` defines the type of font size distribution algorithm +which will be used - logarithmic or linear. It must be either +``tagging.utils.LOGARITHMIC`` (default) or ``tagging.utils.LINEAR``. + +The algorithm to scale the tags logarithmically is from a blog post by +Anders Pearson, `Scaling tag clouds`_. + +.. _`Scaling tag clouds`: http://thraxil.com/users/anders/posts/2005/12/13/scaling-tag-clouds/ + + +Model Fields +============ + +The ``tagging.fields`` module contains fields which make it easy to +integrate tagging into your models and into the +``django.contrib.admin`` application. + +Field types +----------- + +``TagField`` +~~~~~~~~~~~~ + +A ``CharField`` that actually works as a relationship to tags "under +the hood". + +Using this example model:: + + class Link(models.Model): + ... + tags = TagField() + +Setting tags:: + + >>> l = Link.objects.get(...) + >>> l.tags = 'tag1 tag2 tag3' + +Getting tags for an instance:: + + >>> l.tags + 'tag1 tag2 tag3' + +Getting tags for a model - i.e. all tags used by all instances of the +model:: + + >>> Link.tags + 'tag1 tag2 tag3 tag4 tag5' + +This field will also validate that it has been given a valid list of +tag names, separated by a single comma, a single space or a comma +followed by a space, using the ``isTagList`` validator from +``tagging.validators``. + + +Form Fields +=========== + +The ``tagging.forms`` module contains a ``Field`` for use with +Django's `newforms library`_ which takes care of validating tag name +input when used in your forms. + +.. _`newforms library`: http://www.djangoproject.com/documentation/newforms/ + +Field types +----------- + +``TagField`` +~~~~~~~~~~~~ + +A form ``Field`` which is displayed as a single-line text input, which +validates that the input it receives is a valid list of tag names, +separated by a single comma, a single space or a comma followed by a +space. + +When you generate a form for one of your models automatically, using +the ``form_for_model`` or ``form_for_instance`` functions provided by +the newforms library, any ``tagging.fields.TagField`` fields in your +model will automatically be represented by a +``tagging.forms.TagField`` in the generated form. + + +Simplified tagging and retrieval of tags with properties +======================================================== + +If you're not using ``TagField``, a useful method for simplifying +tagging and retrieval of tags for your models is to set up a +property:: + + from django.db import models + from tagging.models import Tag + + class MyModel(models.Model): + name = models.CharField(maxlength=100) + tag_list = models.CharField(maxlength=255) + + def save(self): + super(MyModel, self).save() + self.tags = self.tag_list + + def _get_tags(self): + return Tag.objects.get_for_object(self) + + def _set_tags(self, tag_list): + Tag.objects.update_tags(self, tag_list) + + tags = property(_get_tags, _set_tags) + + def __str__(self): + return self.name + +Once you've set this up, you can access and set tags in a fairly +natural way:: + + >>> obj = MyModel.objects.get(pk=1) + >>> obj.tags = 'foo bar' + >>> obj.tags + [<Tag: bar>, <Tag: foo>] + +Remember that ``obj.tags`` will return a ``QuerySet``, so you can +perform further filtering on it, should you need to. + + +Generic Views +============= + +**New in django-tagging development version** + +The ``tagging.views`` module contains views to handle common display +ogic related to tagging. + +The following sample URLconf demonstrates using a generic view to list +items of a particular model which have a given tag:: + + from django.conf.urls.defaults import * + from tagging.views import tagged_object_list + from shop.apps.products.models import Widget + + urlpatterns = patterns('', + (r'^widgets/tag/(?P<tag>[^/]+(?u))/$', tagged_object_list, + dict(model=Widget, paginate_by=10, allow_empty=True, + template_object_name='widget')), + ) + +``tagging.views.tagged_object_list`` +------------------------------------ + +**Description:** + +A view that displays a list of objects for a given model which have a +given tag. This is a thin wrapper around the +``django.views.generic.list_detail.object_list`` view, which takes a +model and a tag as its arguments (in addition to the other optional +arguments supported by ``object_list``), building the appropriate +``QuerySet`` for you instead of expecting one to be passed in. + +**Required arguments:** + + * ``model``: The Django model class of the object that will be + listed. + + * ``tag``: The tag which objects of the given model must have in + order to be listed. + +**Optional arguments:** + +Please refer to the `object_list documentation`_ for additional optional +arguments which may be given. + + * ``related_tags``: If ``True``, a ``related_tags`` context variable + will also contain tags related to the given tag for the given + model. + + * ``related_tag_counts``: If ``True`` and ``related_tags`` is + ``True``, each related tag will have a ``count`` attribute + indicating the number of items which have it in addition to the + given tag. + +**Template context:** + + * ``tag``: The ``Tag`` instance for the given tag. + +Please refer to the `object_list documentation`_ for additional +template context variables which may be provided. + +.. _`object_list documentation`: http://www.djangoproject.com/documentation/generic_views/#django-views-generic-list-detail-object-list + +Template tags +============= + +The ``tagging.templatetags.tagging_tags`` module defines a number of +template tags which may be used to work with tags. + +Tag reference +------------- + +tags_for_model +~~~~~~~~~~~~~~ + +Retrieves a list of tags associated with the given model and stores +them in a context variable. + +The model is specified in ``[appname].[modelname]`` format. + +If specified - by providing extra ``with counts`` arguments - adds a +``count`` attribute to each tag containing the number of instances of +the given model which have been tagged with it. + +Example usage:: + + {% tags_for_model products.Widget as widget_tags %} + + {% tags_for_model products.Widget as widget_tags with counts %} + +tags_for_object +~~~~~~~~~~~~~~~ + +Retrieves a list of tags associated with an object and stores them in +a context variable. + +Example usage:: + + {% tags_for_object widget as tag_list %} + +tagged_objects +~~~~~~~~~~~~~~ + +Retrieves a list of objects for a given model which are tagged with +a given tag and stores them in a context variable. + +The tag must be an instance of a ``Tag``, not the name of a tag. + +The model is specified in ``[appname].[modelname]`` format. + +Example usage:: + + {% tagged_objects house_tag in products.Widget as widgets %}
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