| | .. currentmodule:: flask |
| |
|
| | Templates |
| | ========= |
| |
|
| | You've written the authentication views for your application, but if |
| | you're running the server and try to go to any of the URLs, you'll see a |
| | ``TemplateNotFound`` error. That's because the views are calling |
| | :func:`render_template`, but you haven't written the templates yet. |
| | The template files will be stored in the ``templates`` directory inside |
| | the ``flaskr`` package. |
| |
|
| | Templates are files that contain static data as well as placeholders |
| | for dynamic data. A template is rendered with specific data to produce a |
| | final document. Flask uses the `Jinja`_ template library to render |
| | templates. |
| |
|
| | In your application, you will use templates to render `HTML`_ which |
| | will display in the user's browser. In Flask, Jinja is configured to |
| | *autoescape* any data that is rendered in HTML templates. This means |
| | that it's safe to render user input; any characters they've entered that |
| | could mess with the HTML, such as ``<`` and ``>`` will be *escaped* with |
| | *safe* values that look the same in the browser but don't cause unwanted |
| | effects. |
| |
|
| | Jinja looks and behaves mostly like Python. Special delimiters are used |
| | to distinguish Jinja syntax from the static data in the template. |
| | Anything between ``{{`` and ``}}`` is an expression that will be output |
| | to the final document. ``{%`` and ``%}`` denotes a control flow |
| | statement like ``if`` and ``for``. Unlike Python, blocks are denoted |
| | by start and end tags rather than indentation since static text within |
| | a block could change indentation. |
| |
|
| | .. _Jinja: https://jinja.palletsprojects.com/templates/ |
| | .. _HTML: https://developer.mozilla.org/docs/Web/HTML |
| |
|
| |
|
| | The Base Layout |
| | --------------- |
| |
|
| | Each page in the application will have the same basic layout around a |
| | different body. Instead of writing the entire HTML structure in each |
| | template, each template will *extend* a base template and override |
| | specific sections. |
| |
|
| | .. code-block:: html+jinja |
| | :caption: ``flaskr/templates/base.html`` |
| |
|
| | <!doctype html> |
| | <title>{% block title %}{% endblock %} - Flaskr</title> |
| | <link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}"> |
| | <nav> |
| | <h1>Flaskr</h1> |
| | <ul> |
| | {% if g.user %} |
| | <li><span>{{ g.user['username'] }}</span> |
| | <li><a href="{{ url_for('auth.logout') }}">Log Out</a> |
| | {% else %} |
| | <li><a href="{{ url_for('auth.register') }}">Register</a> |
| | <li><a href="{{ url_for('auth.login') }}">Log In</a> |
| | {% endif %} |
| | </ul> |
| | </nav> |
| | <section class="content"> |
| | <header> |
| | {% block header %}{% endblock %} |
| | </header> |
| | {% for message in get_flashed_messages() %} |
| | <div class="flash">{{ message }}</div> |
| | {% endfor %} |
| | {% block content %}{% endblock %} |
| | </section> |
| |
|
| | :data:`g` is automatically available in templates. Based on if |
| | ``g.user`` is set (from ``load_logged_in_user``), either the username |
| | and a log out link are displayed, or links to register and log in |
| | are displayed. :func:`url_for` is also automatically available, and is |
| | used to generate URLs to views instead of writing them out manually. |
| |
|
| | After the page title, and before the content, the template loops over |
| | each message returned by :func:`get_flashed_messages`. You used |
| | :func:`flash` in the views to show error messages, and this is the code |
| | that will display them. |
| |
|
| | There are three blocks defined here that will be overridden in the other |
| | templates: |
| |
|
| | #. ``{% block title %}`` will change the title displayed in the |
| | browser's tab and window title. |
| |
|
| | #. ``{% block header %}`` is similar to ``title`` but will change the |
| | title displayed on the page. |
| |
|
| | #. ``{% block content %}`` is where the content of each page goes, such |
| | as the login form or a blog post. |
| |
|
| | The base template is directly in the ``templates`` directory. To keep |
| | the others organized, the templates for a blueprint will be placed in a |
| | directory with the same name as the blueprint. |
| |
|
| |
|
| | Register |
| | -------- |
| |
|
| | .. code-block:: html+jinja |
| | :caption: ``flaskr/templates/auth/register.html`` |
| |
|
| | {% extends 'base.html' %} |
| |
|
| | {% block header %} |
| | <h1>{% block title %}Register{% endblock %}</h1> |
| | {% endblock %} |
| |
|
| | {% block content %} |
| | <form method="post"> |
| | <label for="username">Username</label> |
| | <input name="username" id="username" required> |
| | <label for="password">Password</label> |
| | <input type="password" name="password" id="password" required> |
| | <input type="submit" value="Register"> |
| | </form> |
| | {% endblock %} |
| |
|
| | ``{% extends 'base.html' %}`` tells Jinja that this template should |
| | replace the blocks from the base template. All the rendered content must |
| | appear inside ``{% block %}`` tags that override blocks from the base |
| | template. |
| | |
| | A useful pattern used here is to place ``{% block title %}`` inside |
| | ``{% block header %}``. This will set the title block and then output |
| | the value of it into the header block, so that both the window and page |
| | share the same title without writing it twice. |
| |
|
| | The ``input`` tags are using the ``required`` attribute here. This tells |
| | the browser not to submit the form until those fields are filled in. If |
| | the user is using an older browser that doesn't support that attribute, |
| | or if they are using something besides a browser to make requests, you |
| | still want to validate the data in the Flask view. It's important to |
| | always fully validate the data on the server, even if the client does |
| | some validation as well. |
| |
|
| |
|
| | Log In |
| | ------ |
| |
|
| | This is identical to the register template except for the title and |
| | submit button. |
| |
|
| | .. code-block:: html+jinja |
| | :caption: ``flaskr/templates/auth/login.html`` |
| |
|
| | {% extends 'base.html' %} |
| |
|
| | {% block header %} |
| | <h1>{% block title %}Log In{% endblock %}</h1> |
| | {% endblock %} |
| |
|
| | {% block content %} |
| | <form method="post"> |
| | <label for="username">Username</label> |
| | <input name="username" id="username" required> |
| | <label for="password">Password</label> |
| | <input type="password" name="password" id="password" required> |
| | <input type="submit" value="Log In"> |
| | </form> |
| | {% endblock %} |
| |
|
| |
|
| | Register A User |
| | --------------- |
| |
|
| | Now that the authentication templates are written, you can register a |
| | user. Make sure the server is still running (``flask run`` if it's not), |
| | then go to http://127.0.0.1:5000/auth/register. |
| |
|
| | Try clicking the "Register" button without filling out the form and see |
| | that the browser shows an error message. Try removing the ``required`` |
| | attributes from the ``register.html`` template and click "Register" |
| | again. Instead of the browser showing an error, the page will reload and |
| | the error from :func:`flash` in the view will be shown. |
| |
|
| | Fill out a username and password and you'll be redirected to the login |
| | page. Try entering an incorrect username, or the correct username and |
| | incorrect password. If you log in you'll get an error because there's |
| | no ``index`` view to redirect to yet. |
| |
|
| | Continue to :doc:`static`. |
| |
|
