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@ -1,5 +1,5 @@
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Form Media
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==========
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Form Assets (the ``Media`` class)
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=================================
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Rendering an attractive and easy-to-use Web form requires more than just
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HTML - it also requires CSS stylesheets, and if you want to use fancy
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@ -7,23 +7,24 @@ HTML - it also requires CSS stylesheets, and if you want to use fancy
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page. The exact combination of CSS and JavaScript that is required for
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any given page will depend upon the widgets that are in use on that page.
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This is where Django media definitions come in. Django allows you to
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associate different media files with the forms and widgets that require
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that media. For example, if you want to use a calendar to render DateFields,
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you can define a custom Calendar widget. This widget can then be associated
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with the CSS and JavaScript that is required to render the calendar. When
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the Calendar widget is used on a form, Django is able to identify the CSS and
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This is where asset definitions come in. Django allows you to
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associate different files -- like stylesheets and scripts -- with the
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forms and widgets that require those assets. For example, if you want
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to use a calendar to render DateFields, you can define a custom
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Calendar widget. This widget can then be associated with the CSS and
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JavaScript that is required to render the calendar. When the Calendar
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widget is used on a form, Django is able to identify the CSS and
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JavaScript files that are required, and provide the list of file names
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in a form suitable for easy inclusion on your Web page.
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.. admonition:: Media and Django Admin
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.. admonition:: Assets and Django Admin
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The Django Admin application defines a number of customized widgets
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for calendars, filtered selections, and so on. These widgets define
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media requirements, and the Django Admin uses the custom widgets
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in place of the Django defaults. The Admin templates will only include
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those media files that are required to render the widgets on any
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given page.
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The Django Admin application defines a number of customized
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widgets for calendars, filtered selections, and so on. These
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widgets define asset requirements, and the Django Admin uses the
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custom widgets in place of the Django defaults. The Admin
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templates will only include those files that are required to
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render the widgets on any given page.
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If you like the widgets that the Django Admin application uses,
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feel free to use them in your own application! They're all stored
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@ -38,14 +39,14 @@ in a form suitable for easy inclusion on your Web page.
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whichever toolkit suits your requirements. Django is able to integrate
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with any JavaScript toolkit.
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.. _media-as-a-static-definition:
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.. _assets-as-a-static-definition:
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Media as a static definition
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----------------------------
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Assets as a static definition
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-----------------------------
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The easiest way to define media is as a static definition. Using this method,
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the media declaration is an inner class. The properties of the inner class
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define the media requirements.
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The easiest way to define assets is as a static definition. Using this
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method, the declaration is an inner ``Media`` class. The properties of the
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inner class define the requirements.
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Here's a simple example::
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@ -63,9 +64,9 @@ Every time the CalendarWidget is used on a form, that form will be directed
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to include the CSS file ``pretty.css``, and the JavaScript files
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``animations.js`` and ``actions.js``.
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This static media definition is converted at runtime into a widget property
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named ``media``. The media for a CalendarWidget instance can be retrieved
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through this property::
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This static definition is converted at runtime into a widget property
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named ``media``. The list of assets for a ``CalendarWidget`` instance
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can be retrieved through this property::
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>>> w = CalendarWidget()
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>>> print(w.media)
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@ -82,8 +83,8 @@ A dictionary describing the CSS files required for various forms of output
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media.
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The values in the dictionary should be a tuple/list of file names. See
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:ref:`the section on media paths <form-media-paths>` for details of how to
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specify paths to media files.
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:ref:`the section on paths <form-asset-paths>` for details of how to
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specify paths to these files.
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The keys in the dictionary are the output media types. These are the same
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types accepted by CSS files in media declarations: 'all', 'aural', 'braille',
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@ -119,19 +120,20 @@ If this last CSS definition were to be rendered, it would become the following H
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``js``
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~~~~~~
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A tuple describing the required JavaScript files. See :ref:`the section on
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media paths <form-media-paths>` for details of how to specify paths to media
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files.
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A tuple describing the required JavaScript files. See :ref:`the
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section on paths <form-asset-paths>` for details of how to specify
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paths to these files.
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``extend``
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~~~~~~~~~~
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A boolean defining inheritance behavior for media declarations.
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A boolean defining inheritance behavior for ``Media`` declarations.
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By default, any object using a static media definition will inherit all the
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media associated with the parent widget. This occurs regardless of how the
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parent defines its media requirements. For example, if we were to extend our
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basic Calendar widget from the example above::
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By default, any object using a static ``Media`` definition will
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inherit all the assets associated with the parent widget. This occurs
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regardless of how the parent defines its own requirements. For
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example, if we were to extend our basic Calendar widget from the
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example above::
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>>> class FancyCalendarWidget(CalendarWidget):
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... class Media:
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@ -148,9 +150,9 @@ basic Calendar widget from the example above::
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<script type="text/javascript" src="http://static.example.com/actions.js"></script>
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<script type="text/javascript" src="http://static.example.com/whizbang.js"></script>
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The FancyCalendar widget inherits all the media from its parent widget. If
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you don't want media to be inherited in this way, add an ``extend=False``
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declaration to the media declaration::
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The FancyCalendar widget inherits all the assets from its parent
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widget. If you don't want ``Media`` to be inherited in this way, add
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an ``extend=False`` declaration to the ``Media`` declaration::
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>>> class FancyCalendarWidget(CalendarWidget):
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... class Media:
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@ -165,23 +167,24 @@ declaration to the media declaration::
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<link href="http://static.example.com/fancy.css" type="text/css" media="all" rel="stylesheet" />
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<script type="text/javascript" src="http://static.example.com/whizbang.js"></script>
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If you require even more control over media inheritance, define your media
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using a :ref:`dynamic property <dynamic-property>`. Dynamic properties give
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you complete control over which media files are inherited, and which are not.
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If you require even more control over inheritance, define your assets using a
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:ref:`dynamic property <dynamic-property>`. Dynamic properties give you
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complete control over which files are inherited, and which are not.
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.. _dynamic-property:
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Media as a dynamic property
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---------------------------
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``Media`` as a dynamic property
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-------------------------------
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If you need to perform some more sophisticated manipulation of media
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requirements, you can define the media property directly. This is done
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by defining a widget property that returns an instance of ``forms.Media``.
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The constructor for ``forms.Media`` accepts ``css`` and ``js`` keyword
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arguments in the same format as that used in a static media definition.
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If you need to perform some more sophisticated manipulation of asset
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requirements, you can define the ``media`` property directly. This is
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done by defining a widget property that returns an instance of
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``forms.Media``. The constructor for ``forms.Media`` accepts ``css``
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and ``js`` keyword arguments in the same format as that used in a
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static media definition.
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For example, the static media definition for our Calendar Widget could
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also be defined in a dynamic fashion::
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For example, the static definition for our Calendar Widget could also
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be defined in a dynamic fashion::
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class CalendarWidget(forms.TextInput):
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def _media(self):
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@ -190,17 +193,17 @@ also be defined in a dynamic fashion::
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media = property(_media)
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See the section on `Media objects`_ for more details on how to construct
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return values for dynamic media properties.
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return values for dynamic ``media`` properties.
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.. _form-media-paths:
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.. _form-asset-paths:
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Paths in media definitions
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Paths in asset definitions
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--------------------------
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Paths used to specify media can be either relative or absolute. If a path
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starts with ``/``, ``http://`` or ``https://``, it will be interpreted as an
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absolute path, and left as-is. All other paths will be prepended with the value
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of the appropriate prefix.
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Paths used to specify assets can be either relative or absolute. If a
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path starts with ``/``, ``http://`` or ``https://``, it will be
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interpreted as an absolute path, and left as-is. All other paths will
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be prepended with the value of the appropriate prefix.
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As part of the introduction of the
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:doc:`staticfiles app </ref/contrib/staticfiles>` two new settings were added
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@ -236,21 +239,22 @@ But if :setting:`STATIC_URL` is ``'http://static.example.com/'``::
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<script type="text/javascript" src="http://othersite.com/actions.js"></script>
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Media objects
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-------------
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``Media`` objects
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-----------------
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When you interrogate the media attribute of a widget or form, the value that
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is returned is a ``forms.Media`` object. As we have already seen, the string
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representation of a Media object is the HTML required to include media
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in the ``<head>`` block of your HTML page.
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When you interrogate the ``media`` attribute of a widget or form, the
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value that is returned is a ``forms.Media`` object. As we have already
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seen, the string representation of a ``Media`` object is the HTML
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required to include the relevant files in the ``<head>`` block of your
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HTML page.
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However, Media objects have some other interesting properties.
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However, ``Media`` objects have some other interesting properties.
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Media subsets
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~~~~~~~~~~~~~
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Subsets of assets
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~~~~~~~~~~~~~~~~~
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If you only want media of a particular type, you can use the subscript operator
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to filter out a medium of interest. For example::
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If you only want files of a particular type, you can use the subscript
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operator to filter out a medium of interest. For example::
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>>> w = CalendarWidget()
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>>> print(w.media)
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@ -261,14 +265,15 @@ to filter out a medium of interest. For example::
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>>> print(w.media)['css']
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<link href="http://static.example.com/pretty.css" type="text/css" media="all" rel="stylesheet" />
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When you use the subscript operator, the value that is returned is a new
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Media object -- but one that only contains the media of interest.
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When you use the subscript operator, the value that is returned is a
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new ``Media`` object -- but one that only contains the media of interest.
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Combining media objects
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~~~~~~~~~~~~~~~~~~~~~~~
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Combining ``Media`` objects
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Media objects can also be added together. When two media objects are added,
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the resulting Media object contains the union of the media from both files::
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``Media`` objects can also be added together. When two ``Media`` objects are
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added, the resulting ``Media`` object contains the union of the assets
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specified by both::
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>>> from django import forms
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>>> class CalendarWidget(forms.TextInput):
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@ -290,17 +295,19 @@ the resulting Media object contains the union of the media from both files::
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<script type="text/javascript" src="http://static.example.com/actions.js"></script>
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<script type="text/javascript" src="http://static.example.com/whizbang.js"></script>
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Media on Forms
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--------------
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``Media`` on Forms
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------------------
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Widgets aren't the only objects that can have media definitions -- forms
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can also define media. The rules for media definitions on forms are the
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same as the rules for widgets: declarations can be static or dynamic;
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path and inheritance rules for those declarations are exactly the same.
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Widgets aren't the only objects that can have ``media`` definitions --
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forms can also define ``media``. The rules for ``media`` definitions
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on forms are the same as the rules for widgets: declarations can be
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static or dynamic; path and inheritance rules for those declarations
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are exactly the same.
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Regardless of whether you define a media declaration, *all* Form objects
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have a media property. The default value for this property is the result
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of adding the media definitions for all widgets that are part of the form::
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Regardless of whether you define a ``media`` declaration, *all* Form
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objects have a ``media`` property. The default value for this property
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is the result of adding the ``media`` definitions for all widgets that
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are part of the form::
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>>> from django import forms
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>>> class ContactForm(forms.Form):
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@ -314,8 +321,9 @@ of adding the media definitions for all widgets that are part of the form::
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<script type="text/javascript" src="http://static.example.com/actions.js"></script>
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<script type="text/javascript" src="http://static.example.com/whizbang.js"></script>
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If you want to associate additional media with a form -- for example, CSS for form
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layout -- simply add a media declaration to the form::
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If you want to associate additional assets with a form -- for example,
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CSS for form layout -- simply add a ``Media`` declaration to the
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form::
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>>> class ContactForm(forms.Form):
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... date = DateField(widget=CalendarWidget)
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