What about Ajax?¶
Refreshing an individual Widget¶
You can build a Widget which gets refreshed
without reloading the entire page.
The tutorial.ajaxbootstrap example has Nav and a Div. The
contents of the Div changes each time an item is selected on the
Nav without reloading the entire page.
Only HTMLElements can refresh. To let an HTMLElement refresh, it
needs arguments and needs to call
enable_refresh() in its __init__
method.
In the example, RefreshedPanel is given arguments in an
exposed method named
query_fields(). Each argument is defined by
assigning a Field to an attribute of fields:
@exposed
def query_fields(self, fields):
fields.selected = IntegerField(required=False, default=1)
This makes the value of self.selected available in RefreshedPanel.__init__ to be
used when generating the RefreshedPanel (self.selected is set from
the URL or the default of the Field):
class RefreshedPanel(Div):
def __init__(self, view, css_id):
super(RefreshedPanel, self).__init__(view, css_id=css_id)
self.add_child(P(view, text='You selected link number %s' % self.selected))
self.enable_refresh()
A special “in-page” Bookmark refers to a Widget on the current
UrlBoundView, but with different argument values.
Construct such a Bookmark for a given value of selected by calling
for_widget() with suitable
query_arguments. Before using the Bookmark, call
on_view() to bind it to the current
View.
def get_bookmark(self, for_selected):
return Bookmark.for_widget('Select %s' % for_selected, query_arguments={'selected': for_selected}).on_view(self.view)
Use such bound Bookmarks as usual:
class HomePanel(Div):
def __init__(self, view):
super(HomePanel, self).__init__(view)
panel = RefreshedPanel(view, 'my_refreshedpanel')
bookmarks = [panel.get_bookmark(1),
panel.get_bookmark(2),
panel.get_bookmark(3)]
self.add_child(H(view, 1, text='Refreshing widget'))
self.add_child(Nav(view).use_layout(TabLayout()).with_bookmarks(bookmarks))
self.add_child(panel)
Note
If a Widget declares query_fields, it must have a unique css_id.
Paging long lists¶
The tutorial.pagerbootstrap example lets a user page though a very long list of Addresses, displaying only a managable number at a time.
Three objects play a role in this scenario:
- A
SequentialPageIndexbreaks the long list of Addresses into separate chunks. - AddressList is a
PagedPanel—it displays the appropriate chunk of Addresses (itscurrent_contents()). - An accompanying
PageMenuallows the user to navigate.
class AddressBookPanel(Div):
def __init__(self, view):
super(AddressBookPanel, self).__init__(view)
self.add_child(H(view, 1, text='Addresses'))
self.page_index = SequentialPageIndex(Address.all_addresses(), items_per_page=5)
self.address_list = AddressList(view, self.page_index)
self.page_menu = PageMenu(view, 'page_menu', self.page_index, self.address_list)
self.add_children([self.page_menu, self.address_list])
Since AddressList is a PagedPanel, it automatically refreshes and
computes its current_contents based on the given
SequentialPageIndex.
class AddressList(PagedPanel):
def __init__(self, view, page_index):
super(AddressList, self).__init__(view, page_index, 'addresslist')
for address in self.current_contents:
self.add_child(P(view, text='%s: %s' % (address.name, address.email_address)))
Other implementations of PageIndex are possible, such as
AnnualPageIndex which arranges all items with the same year
together.
