How to determine if a specific value exists in an array (slice) while developing an AnQi CMS template?

During the development of AnQi CMS templates, we often encounter the need to determine whether an array (slice) contains a specific value.For example, you may need to dynamically adjust the display of content based on whether a user tag exists in a predefined tag list;Or when handling complex business logic, determine if a permission ID exists in the current user's permission set.For this kind of requirement, AnQiCMS template engine provides a simple and powerful solution, allowing developers to handle these logic in an elegant way.

In the AnQiCMS template system, we do not need to write complex loops to compare array elements one by one. Thanks to its built-in rich filters, we can use them directlycontainThe filter can easily complete this task. This filter is designed to be very intuitive, and its core function is to determine whether an object (which can be a string, array, Map, or structure) contains a certain keyword and return a boolean value (TrueorFalse)

Deep understandingcontainFilter

containThe filter is a very practical tool in the AnQiCMS template engine, which can efficiently check whether a collection or string contains the specified content.When applied to an array (slice), it checks if there is an element value that matches the provided "keyword" exactly.The returned boolean value can be directly used for conditional judgment in the template(ifSentences), thus achieving dynamic content display.

Actual operation: How to determine if a value exists in an array (slice)?

Let's demonstrate through a specific example.containThe usage of the filter to determine if a value exists in an array (slice).

Assuming we have a variable named in the template context of AnQiCMS.user_tagsAn array that contains all the tags currently owned by the user, for example:["VIP", "推广大使", "活跃用户"]Now, we want to determine if the user has the 'VIP' tag.

{# 假设 user_tags 是一个包含用户标签的数组 #}
{% set user_tags = ["VIP", "推广大使", "活跃用户"] %}

{# 使用 contain 过滤器判断是否存在“VIP”标签 #}
{% if user_tags|contain:"VIP" %}
    <p>恭喜您，您是我们的尊贵VIP用户！</p>
    <a href="/vip-exclusive-content">查看VIP专属内容</a>
{% else %}
    <p>您还不是VIP用户，立即升级享受更多特权！</p>
    <a href="/upgrade-to-vip">升级VIP</a>
{% endif %}

In the code above:

1. We first pass through{% set user_tags = ["VIP", "推广大使", "活跃用户"] %}Defined a nameduser_tagsAn array. In practical applications,user_tagsThis is usually passed to the template by the backend logic.
2. Next, we use{% if user_tags|contain:"VIP" %}to make conditional judgments.user_tags|contain:"VIP"This part iscontainThe application of the filter, it will checkuser_tagsif there is a string in the array"VIP".
3. If it exists, the condition judgment result isTrueIt will then display content such as 'Congratulations, you are our esteemed VIP user!'.
4. If it does not exist, the condition judgment result isFalseThis will display content such as 'You are not a VIP user...' etc.

This approach avoids the麻烦 of manually traversing the array, making the template code more concise, readable, and efficient.

It is not just an array:containThe extensive application scenarios of filters

containThe filter is not only effective for arrays (slice), but its strength lies in its broad applicability. It can be applied to various data types to meet different judgment needs:

• Determine if a string contains a substring:You can check if a longer text string contains a specific keyword.

  
  {% set article_title = "安企CMS：打造高效内容管理体验" %}
  {% if article_title|contain:"CMS" %}
      <p>标题中包含关键词“CMS”。</p>
  {% endif %}
  

• Determine if a Map or structure contains a specific key name: containThe filter can also be used to check if a Map (key-value set) or structure contains a specified key name (key).

  
  {% set product_info = {"name": "安企CMS", "version": "3.0", "price": 0} %}
  {% if product_info|contain:"version" %}
      <p>产品信息中包含版本号。</p>
  {% endif %}
  

  It should be noted that when used with Map or structure,containThe check is whether the key name (key) exists, not whether a value (value) exists in any key of the Map.

Summary

AnQiCMS template engine'scontainThe filter brings great convenience to template development. It provides a declarative, efficient, and easy-to-understand way to determine whether a specific content exists in an array (slice), string, Map, or struct.By flexible usecontainThe filter, we can write more dynamic, logical and stronger AnQiCMS templates, thus enhancing the website's interactive experience and the efficiency of content operation.

Frequently Asked Questions (FAQ)

Q1: How to determine if an array does not contain a specific value? A1:If you want to determine if an array does not contain a specific value, just add in front ofcontainthe filter's resultnotthe keyword.

{% set user_roles = ["Admin", "Editor"] %}
{% if not user_roles|contain:"Guest" %}
    <p>用户不是访客。</p>
{% endif %}

Q2: Can I also get the specific 'position' of this value in the array besides checking for its existence? A2:Yes. You can use the AnQiCMS template engine provided.indexA filter to get the first occurrence position of a value in an array (slice) or string. If not found, it will return-1.

{% set product_ids = [101, 105, 110, 105] %}
{% set position = product_ids|index:105 %}
<p>值105在数组中首次出现的位置是：{{ position }}</p> {# 输出：1 (数组索引从0开始) #}

{% set not_found_position = product_ids|index:999 %}
<p>值999在数组中首次出现的位置是：{{ not_found_position }}</p> {# 输出：-1 #}

Q3: If there may be multiple identical values in an array, how can I know how many times it appears? A3:You can usecountA filter to count the number of times a specific value appears in an array (slice) or string.

{% set status_list = ["pending", "approved", "rejected", "approved"] %}
{% set approved_count = status_list|count:"approved" %}
<p>“approved”状态出现了：{{ approved_count }} 次。</p> {# 输出：2 #}

{% set article_text = "AnQiCMS 是一个强大的CMS，AnQiCMS让内容管理更简单。" %}
{% set cms_count = article_text|count:"CMS" %}
<p>“CMS”在文本中出现了：{{ cms_count }} 次。</p> {# 输出：2 #}