# Functions

URL: /docs/syntax/functions/
Section: syntax
Tags: syntax, functions, macros

--------------------------------------------------------------------------------

Functions Define reusable template functions within your templates. Defining Functions Use {% def %} to create a function: {% def greet(name) %} <p>Hello, {{ name }}!</p> {% end %} {{ greet("Alice") }} {{ greet("Bob") }} Parameters Required Parameters {% def button(text, url) %} <a href="{{ url }}" class="button">{{ text }}</a> {% end %} {{ button("Click Me", "/action") }} Default Values {% def button(text, url, style="primary") %} <a href="{{ url }}" class="button button-{{ style }}">{{ text }}</a> {% end %} {{ button("Save", "/save") }} {{ button("Cancel", "/cancel", style="secondary") }} Keyword Arguments {% def card(title, content="", footer=none) %} <div class="card"> <h3>{{ title }}</h3> {% if content %} <p>{{ content }}</p> {% end %} {% if footer %} <footer>{{ footer }}</footer> {% end %} </div> {% end %} {{ card(title="Hello", content="World") }} {{ card("Title Only") }} Capturing Content Functions can capture block content using caller(): {% def wrapper(title) %} <section> <h2>{{ title }}</h2> <div class="content"> {{ caller() }} </div> </section> {% end %} {% call wrapper("Section Title") %} <p>This content is passed to the wrapper.</p> <ul> <li>Item 1</li> <li>Item 2</li> </ul> {% end %} Macros Kida also supports the {% macro %} syntax: {% macro input(name, value="", type="text") %} <input type="{{ type }}" name="{{ name }}" value="{{ value }}"> {% endmacro %} {{ input("username") }} {{ input("password", type="password") }} Importing Functions Import functions from other templates: {% from "macros.html" import button, input %} {{ button("Submit", "/submit") }} {{ input("email", type="email") }} Import all with a namespace: {% import "forms.html" as forms %} {{ forms.input("name") }} {{ forms.textarea("bio") }} Best Practices Single Responsibility Each function should do one thing: {# Good: Single purpose #} {% def user_avatar(user, size=32) %} <img src="{{ user.avatar_url }}" alt="{{ user.name }}" width="{{ size }}" height="{{ size }}"> {% end %} {# Avoid: Too much logic #} {% def user_card_with_everything(user, show_bio, show_posts, ...) %} ... {% end %} Descriptive Names {# Good: Clear purpose #} {% def format_price(amount, currency="USD") %} {% def user_badge(role) %} {% def pagination_nav(current, total) %} {# Avoid: Vague names #} {% def render(x) %} {% def do_thing(item) %} See Also Inheritance — Extend base templates Includes — Include partials Custom Filters — Python-defined filters

--------------------------------------------------------------------------------

Metadata:
- Word Count: 358
- Reading Time: 2 minutes