How to use the `not` operator to reverse conditional judgments in AnQiCMS templates?
AnQiCMS's template system is known for its flexibility and efficiency, drawing inspiration from the syntax style of Django template engine, making content presentation and logic control intuitive.In template development, we often need to display or hide content based on different conditions, at this time, mastering various usage of conditional judgment is particularly important.Today, let's talk about how to cleverly use the AnQiCMS templatenotThe operator to reverse the conditional judgment, making your page logic clearer and more flexible.
What isnotOperator ?
In any programming language,notOperators play the role of 'not', with a very simple function: to reverse the result of a boolean expression (true or false). If a condition was originally true (True), afternotAfter processing it will become false; conversely, if the condition is false, it will become true.
In the AnQiCMS template,not主要用于{% if %}Inside the tag, it helps us construct reverse logical judgments. This can make the code intent clearer in many scenarios or solve some complex logical problems directly.
Basic usage
notThe basic syntax of operators is very intuitive:
{% if not 你的条件 %}
<!-- 当“你的条件”为假时，这里的内容会显示 -->
{% endif %}
Or, if you want to execute another block of code when the condition is true, you can combineelse:
{% if not 你的条件 %}
<!-- 当“你的条件”为假时，这里的内容会显示 -->
{% else %}
<!-- 当“你的条件”为真时，这里的内容会显示 -->
{% endif %}
Next, let's take a look at some actual scenarios from several AnQiCMS templatesnotWhat conveniences can it bring.
Practical Scenarios and Examples
1. Display alternate content or placeholders
Imagine that your articles may not all have thumbnails. Whenarchive.Thumb(Document thumbnail) If it does not exist or is empty, you want to display a default image as a placeholder instead of leaving the page blank.
<a href="{{ archive.Link }}">
{% if not archive.Thumb %}
<img src="/public/static/images/default-thumbnail.webp" alt="默认缩略图">
{% else %}
<img src="{{ archive.Thumb }}" alt="{{ archive.Title }}">
{% endif %}
<h3>{{ archive.Title }}</h3>
</a>
Here, {% if not archive.Thumb %}Will checkarchive.ThumbDoes the value exist. If not (empty or does not exist), the condition is true and the default thumbnail is displayed. If there is, the condition is false and the article's own thumbnail is displayed.
2. Handle inactive states or exclude specific items
In the navigation menu or list display, you may want to handle 'non-current' pages or certain items differently.
For example, in a category list loop, you want to highlight allNotis the link of the currently selected category:
{% categoryList categories with moduleId="1" parentId="0" %}
<ul>
{% for item in categories %}
<li {% if not item.IsCurrent %}class="inactive-category"{% endif %}>
<a href="{{ item.Link }}">{{ item.Title }}</a>
</li>
{% endfor %}
</ul>
{% endcategoryList %}
here,item.IsCurrentIt is a boolean value indicating whether the category being looped over is the one the user is browsing.{% if not item.IsCurrent %}Then it judged 'If this is not the current category', and then added one.inactive-categoryof the CSS class.
For example, you have a list of documents but want to exclude the special document with ID 10:
{% archiveList archives with type="list" limit="10" %}
<ul>
{% for item in archives %}
{% if not item.Id == 10 %}
<li><a href="{{ item.Link }}">{{ item.Title }}</a></li>
{% endif %}
{% endfor %}
</ul>
{% endarchiveList %}
By{% if not item.Id == 10 %}we only render those with IDnot equal toThe article item of 10.
Fine control of website status.
AnQiCMS supports website shutdown functionality, when the website is in shutdown mode, it will usually display a shutdown prompt. You can usenotto control when normal content is displayed:
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title>{% tdk with name="Title" siteName=true %}</title>
</head>
<body>
{% if system.SiteCloseTips %}
<!-- 如果网站处于闭站状态，显示闭站提示 -->
<div class="site-closed-banner">
<p>{{ system.SiteCloseTips }}</p>
</div>
{% else %}
<!-- 如果网站未闭站，则显示正常网站内容 -->
<header>...</header>
<main>
<h1>欢迎访问我们的网站！</h1>
<!-- 其他正常页面内容 -->
</main>
<footer>...</footer>
{% endif %}
</body>
</html>
Although here we used{% if system.SiteCloseTips %}to directly determine if the shutdown prompt exists, but another approach is, ifsystem.SiteCloseTipsIf the variable does not exist (i.e., the website is not closed), it will display normal content, and this can also be achieved throughnotto achieve:
{% if not system.SiteCloseTips %}
<!-- 网站未闭站，显示正常内容 -->
<header>...</header>
<main>...</main>
<footer>...</footer>
{% else %}
<!-- 网站已闭站，显示闭站提示 -->
<div class="site-closed-banner">
<p>{{ system.SiteCloseTips }}</p>
</div>
{% endif %}
This format is also effective, and you can choose according to personal preference or team specifications.
Combineand,orOperator
notThe operator can also be combined with other logical operatorsand/orto build more complex conditional judgments. For example:
{% if not (item.IsFeatured and item.Category == "News") %}
<!-- 如果文章不是“特色”且“新闻”类别，则显示此内容 -->
{% endif %}
Herenot (item.IsFeatured and item.Category == "News")Means: If the articleNotis a featured articleor Notbelongs to the news category, the condition will be met.
Tip: Reduce blank lines in templates
In AnQiCMS templates, like{% if %}This logical tag sometimes generates extra blank lines during rendering, affecting the aesthetics of the HTML structure. To avoid this, you can use at the beginning and/or end of the tag.-Symbol, as shown below:
{%- if not archive.Thumb %}
<img src="/public/static/images/default-thumbnail.webp" alt="默认缩略图">
{%- else %}
<img src="{{ archive.Thumb }}" alt="{{ archive.Title }}">
{%- endif %}
In{%- ifand{%- elseas well as afterwards{%- endif %}add before-It can effectively remove the lines containing these tags and the adjacent whitespace characters, making the final output HTML more compact.
Summary
notThe operator is a simple yet powerful tool in AnQiCMS templates, which helps us process conditional judgments in reverse thinking, making the template logic more flexible and readable. Whether it is to display alternative content, exclude specific items, or control the visibility of page elements,notEvery role can play its unique role. Master its use and