mirror of https://github.com/mitsuhiko/flask.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
119 lines
3.5 KiB
119 lines
3.5 KiB
.. _message-flashing-pattern: |
|
|
|
Message Flashing |
|
================ |
|
|
|
Good applications and user interfaces are all about feedback. If the user |
|
does not get enough feedback they will probably end up hating the |
|
application. Flask provides a really simple way to give feedback to a |
|
user with the flashing system. The flashing system basically makes it |
|
possible to record a message at the end of a request and access it next |
|
request and only next request. This is usually combined with a layout |
|
template that does this. |
|
|
|
Simple Flashing |
|
--------------- |
|
|
|
So here is a full example:: |
|
|
|
from flask import flash, redirect, url_for, render_template |
|
|
|
@app.route('/') |
|
def index(): |
|
return render_template('index.html') |
|
|
|
@app.route('/login', methods=['GET', 'POST']) |
|
def login(): |
|
error = None |
|
if request.method == 'POST': |
|
if request.form['username'] != 'admin' or \ |
|
request.form['password'] != 'secret': |
|
error = 'Invalid credentials' |
|
else: |
|
flash('You were successfully logged in') |
|
return redirect(url_for('index')) |
|
return render_template('login.html', error=error) |
|
|
|
And here the ``layout.html`` template which does the magic: |
|
|
|
.. sourcecode:: html+jinja |
|
|
|
<!doctype html> |
|
<title>My Application</title> |
|
{% with messages = get_flashed_messages() %} |
|
{% if messages %} |
|
<ul class=flashes> |
|
{% for message in messages %} |
|
<li>{{ message }}</li> |
|
{% endfor %} |
|
</ul> |
|
{% endif %} |
|
{% endwith %} |
|
{% block body %}{% endblock %} |
|
|
|
And here the index.html template: |
|
|
|
.. sourcecode:: html+jinja |
|
|
|
{% extends "layout.html" %} |
|
{% block body %} |
|
<h1>Overview</h1> |
|
<p>Do you want to <a href="{{ url_for('login') }}">log in?</a> |
|
{% endblock %} |
|
|
|
And of course the login template: |
|
|
|
.. sourcecode:: html+jinja |
|
|
|
{% extends "layout.html" %} |
|
{% block body %} |
|
<h1>Login</h1> |
|
{% if error %} |
|
<p class=error><strong>Error:</strong> {{ error }} |
|
{% endif %} |
|
<form action="" method=post> |
|
<dl> |
|
<dt>Username: |
|
<dd><input type=text name=username value="{{ |
|
request.form.username }}"> |
|
<dt>Password: |
|
<dd><input type=password name=password> |
|
</dl> |
|
<p><input type=submit value=Login> |
|
</form> |
|
{% endblock %} |
|
|
|
Flashing With Categories |
|
------------------------ |
|
|
|
.. versionadded:: 0.3 |
|
|
|
It is also possible to provide categories when flashing a message. The |
|
default category if nothing is provided is ``'message'``. Alternative |
|
categories can be used to give the user better feedback. For example |
|
error messages could be displayed with a red background. |
|
|
|
To flash a message with a different category, just use the second argument |
|
to the :func:`~flask.flash` function:: |
|
|
|
flash(u'Invalid password provided', 'error') |
|
|
|
Inside the template you then have to tell the |
|
:func:`~flask.get_flashed_messages` function to also return the |
|
categories. The loop looks slightly different in that situation then: |
|
|
|
.. sourcecode:: html+jinja |
|
|
|
{% with messages = get_flashed_messages(with_categories=true) %} |
|
{% if messages %} |
|
<ul class=flashes> |
|
{% for category, message in messages %} |
|
<li class="{{ category }}">{{ message }}</li> |
|
{% endfor %} |
|
</ul> |
|
{% endif %} |
|
{% endwith %} |
|
|
|
This is just one example of how to render these flashed messages. One |
|
might also use the category to add a prefix such as |
|
``<strong>Error:</strong>`` to the message.
|
|
|