How to remove HTML tags in AnQiCMS template based on conditions?

In the development and maintenance of website templates, we often encounter the need to determine whether a certain HTML element on a page is displayed based on specific data conditions.For example, an article will only display an image tag if there is a thumbnail, or if a custom field has content, the corresponding block will be rendered.This on-demand display mechanism not only makes the template code more organized, avoids the appearance of empty tags or unnecessary visual elements on the page, but also significantly improves user experience and page loading efficiency.

AnQiCMS uses a template engine with syntax similar to Django's, which provides powerful and flexible conditional judgment and loop control capabilities, allowing us to easily implement these dynamic display logic.Understanding and effectively using these features is the key to building a highly efficient and elegant AnQiCMS website template.

Using conditional judgment tags (if)Precise control of HTML display

AnQiCMS template, the most basic and core conditional control tool isifLabel. Through it, we can decide whether to keep or remove an HTML block based on the existence of variables, specific values, or comparisons between variables.

ifThe basic syntax of tags is:{% if 条件 %} ... {% endif %}. When the condition is true (true),{% if %}and{% endif %}The content between will be rendered; otherwise, this part of the content will be ignored.

For example, on the article detail page, we usually want to display the thumbnail only when the article has one.<img>Label to avoid broken icons or blank placeholders when images are missing. This can be achieved in the following way:

{% if archive.Thumb %}
    <img src="{{archive.Thumb}}" alt="{{archive.Title}}" class="article-thumbnail">
{% endif %}

here,archive.ThumbRepresents the thumbnail path of the article. If this variable has a value (i.e., the thumbnail exists),<img>the tag will be rendered.

Besides the simple existence judgment,ifLabels support more complex logic:

• Multi-branch judgment:Use{% elif 条件 %}and{% else %}Can handle various situations. For example, display different prompts based on the article status:

  {% if archive.Status == 1 %}
      <span class="status-published">已发布</span>
  {% elif archive.Status == 0 %}
      <span class="status-draft">草稿</span>
  {% else %}
      <span class="status-unknown">状态未知</span>
  {% endif %}
  

• Variable comparison:You can compare the value of variables, for example, to determine if an ID is a specific value:{% if archive.Id == 10 %}.

• Logical combination:Useand/or/notPerform logical combination to build finer judgment conditions. For example, only display when the article has a description and the length of the description is greater than a certain value:

  {% if archive.Description and archive.Description|length > 20 %}
      <p class="article-summary">{{archive.Description}}</p>
  {% endif %}
  

  This also useslengthFilter used to get the length of a string, which is very useful when determining if the content is sufficient to display.

Dynamic display in loops and handling of empty lists (forandempty)

When we need to traverse list data (such as article lists, category lists),forLoops are indispensable. AnQiCMS'sforLabels not only support regular loop iteration, but also provideemptya sub-label to handle the special case of an empty list.

its syntax structure is{% for item in 列表 %} ... {% empty %} ... {% endfor %}.

If列表with data,{% for %}and{% empty %}The content between will be rendered repeatedly; if列表It is empty,{% empty %}and{% endfor %}The content between the brackets will be rendered once. This makes it possible to display friendly prompts when there is no data, avoiding the appearance of blank or disordered pages.

For example, in a product display area, if there are no products under the current category, we can display a prompt such as 'No products available':

<div class="product-list">
    {% archiveList products with moduleId="2" categoryId=currentCategory.Id limit="8" %}
        {% for item in products %}
            <div class="product-item">
                <h3><a href="{{item.Link}}">{{item.Title}}</a></h3>
                {% if item.Thumb %}
                    <img src="{{item.Thumb}}" alt="{{item.Title}}">
                {% endif %}
            </div>
        {% empty %}
            <p class="no-products-tip">当前分类暂无产品，敬请期待！</p>
        {% endfor %}
    {% endarchiveList %}
</div>

We can also continue using it inside the loop,ifLabel to determine each list item (item) to make conditional judgments based on its properties, such as the judgment in the above exampleitem.Thumbto display the image.

Optimize template output: remove extra blank lines

When using conditional and loop tags, the template engine may introduce some unnecessary blank lines during rendering, especially between logical tags and HTML tags.This does not affect the page function, but may make the generated HTML source code not as 'clean'.AnQiCMS template engine provides{%-and-%}Such a special marker is used to remove these blank spaces during rendering.

• {%-: Removes all spaces on the left side of the tag (including newline characters).
• -%}: It will remove all whitespace to the right of the tag (including newline characters).

For example, if aifstatement has extra whitespace lines before and after:

{# 原始代码，可能产生空白行 #}
<div>
    {% if archive.Thumb %}
        <img src="{{archive.Thumb}}">
    {% endif %}
</div>

{# 优化后，减少空白行 #}
<div>
{%- if archive.Thumb %}
    <img src="{{archive.Thumb}}">
{%- endif %}
</div>

By adding-The symbol can effectively control the number of blank lines in the generated HTML, making the code more compact.

Data preprocessing and default value strategy

Sometimes, we are not to remove HTML tags completely, but to provide a default value when data is missing to prevent empty variables from being output directly and causing the page display to be ugly