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clean up error handler docs

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David Lord 2017-04-30 08:20:13 -07:00
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docs/patterns/errorpages.rst
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@ -47,31 +47,34 @@ even if the application behaves correctly:
Error Handlers Error Handlers
-------------- --------------
An error handler is a function, just like a view function, but it is An error handler is a function that returns a response when a type of error is
called when an error happens and is passed that error. The error is most raised, similar to how a view is a function that returns a response when a
likely a :exc:`~werkzeug.exceptions.HTTPException`, but in one case it request URL is matched. It is passed the instance of the error being handled,
can be a different error: a handler for internal server errors will be which is most likely a :exc:`~werkzeug.exceptions.HTTPException`. An error
passed other exception instances as well if they are uncaught. handler for "500 Internal Server Error" will be passed uncaught exceptions in
addition to explicit 500 errors.
An error handler is registered with the :meth:`~flask.Flask.errorhandler` An error handler is registered with the :meth:`~flask.Flask.errorhandler`
decorator and the error code of the exception (alternatively, you can use the decorator or the :meth:`~flask.Flask.register_error_handler` method. A handler
:meth:`~flask.Flask.register_error_handler` function, e.g., when you're can be registered for a status code, like 404, or for an exception class.
registering error handlers as part of your Application Factory). Keep in mind
that Flask will *not* set the error code for you, so make sure to also provide
the HTTP status code when returning a response.delete_cookie.
Please note that if you add an error handler for "500 Internal Server The status code of the response will not be set to the handler's code. Make
Error", Flask will not trigger it if it's running in Debug mode. sure to provide the appropriate HTTP status code when returning a response from
a handler.
Here an example implementation for a "404 Page Not Found" exception:: A handler for "500 Internal Server Error" will not be used when running in
debug mode. Instead, the interactive debugger will be shown.
Here is an example implementation for a "404 Page Not Found" exception::
from flask import render_template from flask import render_template
@app.errorhandler(404) @app.errorhandler(404)
def page_not_found(e): def page_not_found(e):
# note that we set the 404 status explicitly
return render_template('404.html'), 404 return render_template('404.html'), 404
And, using an application factory pattern (see :ref:`app-factories`):: When using the :ref:`application factory pattern <app-factories>`::
from flask import Flask, render_template from flask import Flask, render_template
@ -80,18 +83,17 @@ And, using an application factory pattern (see :ref:`app-factories`)::
def create_app(config_filename): def create_app(config_filename):
app = Flask(__name__) app = Flask(__name__)
# ...
app.register_error_handler(404, page_not_found) app.register_error_handler(404, page_not_found)
return app
An example template might be this: An example template might be this:
.. sourcecode:: html+jinja .. sourcecode:: html+jinja
{% extends "layout.html" %} {% extends "layout.html" %}
{% block title %}Page Not Found{% endblock %} {% block title %}Page Not Found{% endblock %}
{% block body %} {% block body %}
<h1>Page Not Found</h1> <h1>Page Not Found</h1>
<p>What you were looking for is just not there. <p>What you were looking for is just not there.
<p><a href="{{ url_for('index') }}">go somewhere nice</a> <p><a href="{{ url_for('index') }}">go somewhere nice</a>
{% endblock %} {% endblock %}