Customised error views¶
The default error view¶
The howtos.customisingerrorpages example simulates a programming error when you click on ‘Submit’.
The config setting reahlsystem.debug = True in reahl.config.py controls how an uncaught Exception in your application is handled.
If reahlsystem.debug = True, then a stacktrace is shown.
If reahlsystem.debug = False, your application renders a default error view
derived from the root UserInterface (set in web.site_root config in
reahl.web.config.py).
The default error view is sufficient in most cases.
This example has its web.site_root set to BreakingUIWithBuiltInErrorPage which demonstrates the default behaviour:
class BreakingUIWithBuiltInErrorPage(BreakingUI):
pass
Supplying a completely customised error view¶
Uncomment web.site_root = ‘BreakingUIWithCustomErrorPage’ in etc/web.config.py to see the example customised error view.
BreakingUIWithCustomErrorPage is a different UserInterface which defines a customised
error view by calling define_error_view() in its assemble():
class BreakingUIWithCustomErrorPage(BreakingUI):
def assemble(self):
super().assemble()
self.define_error_view(CustomErrorPage.factory())
The Widget used in the call to define_error_view() replaces the entire HTML5Page
when the error view is shown. On your Widget, provide a class-side method with the
same name and signature as get_widget_bookmark_for_error(). In your get_widget_bookmark_for_error(),
return a page-internal Bookmark to an instance of your Widget which is parameterised
to display the given error message.
ErrorWidget or ErrorMessageBox() are handy to use for this purpose:
class CustomErrorPage(HTML5Page):
def __init__(self, view):
super().__init__(view)
error_widget = self.body.insert_child(0, ErrorWidget(view))
error_widget.add_child(H(view, 1, text='Oops, something broke'))
error_widget.add_child(P(view, text=error_widget.error_message))
error_widget.add_child(A(view, Url(error_widget.error_source_href), description='Click here to try again'))
@classmethod
def get_widget_bookmark_for_error(cls, error_message, error_source_bookmark):
return ErrorWidget.get_widget_bookmark_for_error(error_message, error_source_bookmark)