| Template Inheritance |
| ==================== |
| |
| The most powerful part of Jinja is template inheritance. Template inheritance |
| allows you to build a base "skeleton" template that contains all the common |
| elements of your site and defines **blocks** that child templates can override. |
| |
| Sounds complicated but is very basic. It's easiest to understand it by starting |
| with an example. |
| |
| |
| Base Template |
| ------------- |
| |
| This template, which we'll call :file:`layout.html`, defines a simple HTML skeleton |
| document that you might use for a simple two-column page. It's the job of |
| "child" templates to fill the empty blocks with content: |
| |
| .. sourcecode:: html+jinja |
| |
| <!doctype html> |
| <html> |
| <head> |
| {% block head %} |
| <link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}"> |
| <title>{% block title %}{% endblock %} - My Webpage</title> |
| {% endblock %} |
| </head> |
| <body> |
| <div id="content">{% block content %}{% endblock %}</div> |
| <div id="footer"> |
| {% block footer %} |
| © Copyright 2010 by <a href="http://domain.invalid/">you</a>. |
| {% endblock %} |
| </div> |
| </body> |
| </html> |
| |
| In this example, the ``{% block %}`` tags define four blocks that child templates |
| can fill in. All the `block` tag does is tell the template engine that a |
| child template may override those portions of the template. |
| |
| Child Template |
| -------------- |
| |
| A child template might look like this: |
| |
| .. sourcecode:: html+jinja |
| |
| {% extends "layout.html" %} |
| {% block title %}Index{% endblock %} |
| {% block head %} |
| {{ super() }} |
| <style type="text/css"> |
| .important { color: #336699; } |
| </style> |
| {% endblock %} |
| {% block content %} |
| <h1>Index</h1> |
| <p class="important"> |
| Welcome on my awesome homepage. |
| {% endblock %} |
| |
| The ``{% extends %}`` tag is the key here. It tells the template engine that |
| this template "extends" another template. When the template system evaluates |
| this template, first it locates the parent. The extends tag must be the |
| first tag in the template. To render the contents of a block defined in |
| the parent template, use ``{{ super() }}``. |
| |
