Tags

apply

The apply tag lets you use filters on a block of template data:

{% apply upper %}
    This text becomes uppercase
{% endapply %}

This means the text "This text becomes uppercase" will be transformed to uppercase when rendered.

for

The for loop lets you iterate over each item in a sequence. Here's a deeper dive into its functionalities:

Basic Looping:

To display a list of users:

Users:
    {% for user in users %}
        - {{ user }}
    {% endfor %}

Using the .. Operator:

This operator can help you iterate over a sequence of numbers or letters:

{% for i in 0..10 %}
    - {{ i }}
{% endfor %}

{% for letter in 'a'..'z' %}
    - {{ letter }}
{% endfor %}

Special Variables in for Loop:

Inside a for loop, you can access:

  • loop.index: Current iteration (1 indexed)

  • loop.index0: Current iteration (0 indexed)

  • loop.revindex: Iterations from the end (1 indexed)

  • loop.revindex0: Iterations from the end (0 indexed)

  • loop.first: True if it's the first iteration

  • loop.last: True if it's the last iteration

  • loop.length: Number of items in the sequence

  • loop.parent: The parent context

{% for user in users %}
    - {{ loop.index }}: {{ user }}
{% endfor %}

Iterating Over Keys or Keys and Values:

{% for key in users|keys %}
    - {{ key }}
{% endfor %}

{% for key, user in users %}
    - {{ key }}: {{ user }}
{% endfor %}

Iterating Over a Subset:

To loop over a subset of values, use the slice filter:

Top Ten Users:
{% for user in users|slice(0, 10) %}
    - {{ user }}
{% endfor %}

if

The if statement allows you to test if an expression evaluates to true.

Simple Conditions:

To test if an expression evaluates to true:

{% if online == false %}
    The website is in maintenance mode. Please, come back later.
{% endif %}

Testing Non-Empty Arrays:

{% if users %}
        {% for user in users %}
            - {{ user }}
        {% endfor %}
{% endif %}

Note: To check if a variable is defined, use if users is defined.

Using the not Operator:

{% if not user.subscribed %}
    User is not subscribed to the mailing list.
{% endif %}

Combining Conditions with and and or:

{% if temperature > 18 and temperature < 27 %}
    It's a nice day for a walk in the park.
{% endif %}

Multiple Branches with elseif and else:

{% if product.stock > 10 %}
   Available
{% elseif product.stock > 0 %}
   Only {{ product.stock }} left!
{% else %}
   Sold-out!
{% endif %}

macro

Macros can be likened to functions in most programming languages. They provide a mechanism for reusing template fragments, ensuring that there's no unnecessary repetition in your code.

Example:

{% macro currencyFormat(amount, currencySymbol = "$") %}
    {{ currencySymbol }}{{ amount|number_format(2, '.', ',') }}
{% endmacro %}

{% macro discountPrice(originalPrice, discountPercentage) %}
    {{ originalPrice * (1 - discountPercentage/100)|number_format(2, '.', ',') }}
{% endmacro %}

{% macro formatDate(dateString, format = "Y-m-d") %}
    {{ dateString|date(format) }}
{% endmacro %}

Every argument passed to a macro can have a default value.

set

You have the capability to assign values to variables. These assignments utilize the set tag and can target multiple variables simultaneously.

Basic Variable Assignment:

Assign the value 'bar' to the variable foo:

{% set foo = 'bar' %}

Subsequently, foo becomes available in the template:

{# displays 'bar' #}
{{ foo }}

Variable Assignment with Expressions:

The value assigned can be any valid expression:

{% set foo = [1, 2] %}
{% set foo = {'foo': 'bar'} %}
{% set foo = 'foo' ~ 'bar' %}

Multiple Variable Assignments:

You can assign to multiple variables simultaneously:

{% set foo, bar = 'foo', 'bar' %}

{# This is equivalent to: #}

{% set foo = 'foo' %}
{% set bar = 'bar' %}

Capturing Chunks of Text:

The set tag can be utilized to capture chunks of text:

{% set foo %}
    ...
{% endset %}

Loop Scope:

Loops are scoped. This means a variable declared inside a loop isn't accessible outside:

{% for item in list %}
    {% set foo = item %}
{% endfor %}

{# foo will NOT be accessible here #}

However, to make the variable available outside, you should declare it prior to the loop:

{% set foo = "" %}
{% for item in list %}
    {% set foo = item %}
{% endfor %}

{# Now, foo is accessible here #}

verbatim

The verbatim tag serves to delineate sections as raw text, ensuring they are not parsed. This can be particularly useful when you wish to showcase template syntax as an example within a template. Here's an illustrative snippet:

{% verbatim %}
    {% for item in items %}
        - {{ item }}
    {% endfor %}
{% endverbatim %}

with

The with tag is utilized to create an inner scope. Any variables defined within this scope will not be visible outside of it.

Basic Usage:

{% with %}
    {% set foo = 42 %}
    {{ foo }} {# foo is 42 inside this block #}
{% endwith %}

Outside the block, the variable foo will no longer be accessible.

Defining Variables with a Hash:

You can also define the variables at the beginning of the with scope by passing a hash:

{% with { foo: 42 } %}
    {{ foo }} {# foo is 42 inside this block #}
{% endwith %}

Again, outside the block, the variable foo will not be visible.

Using Expressions that Resolve to a Hash:

This technique works with any expression that resolves to a hash:

{% set vars = { foo: 42 } %}
{% with vars %}
    ...
{% endwith %}

Limiting Visibility with the only Keyword:

By default, the inner with scope has access to the outer scope context. If you wish to limit the inner scope to only the variables defined within it, use the only keyword:

{% set bar = 'bar' %}
{% with { foo: 42 } only %}
    {# Inside this block, only the foo variable is defined. #}
    {# The bar variable is not accessible. #}
{% endwith %}
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