Shopify Liquid中如何将循环获取的article.tags数组转小写实现标签匹配？

问题原因 #

• Liquid的downcase过滤器仅支持对字符串生效，article.tags是数组类型，直接应用过滤器不会生效
• 你之前在for循环外调用article.tags时，循环还未执行，article变量尚未定义，自然无法拿到对应文章的标签数据

修复方案（二选一即可） #

方案1：标签数组转小写字符串匹配（写法简洁） #

通过join过滤器先把标签数组转为字符串再做大小写转换，为了避免部分匹配（比如匹配bag时误命中bagpack），可以给字符串和目标标签前后都加上分隔符做精准匹配：

{% assign taggs = "T-shirt,bag,Purse,Handbag" | split: "," %}
{%- assign length = b_s.related_article_blog_count | plus: 0 -%}
{% capture fourthtag %}{{ taggs[3] | downcase }}{% endcapture %}
<!-- 给目标标签前后加逗号，用于精准匹配 -->
{% assign target_tag = "," | append: fourthtag | append: "," %}
<div class="jj-post-content">
  <div class="item">
    {%- for article in blogs[blog].articles limit: length -%}
      <!-- 把当前文章的标签转成逗号分隔的全小写字符串，前后加逗号 -->
      {% assign article_tags_str = article.tags | join: "," | downcase | prepend: "," | append: "," %}
      {% if article_tags_str contains target_tag %}
        <a href="{{ article.url }}">
          <div class="jj-title">{{ article.title }}</div>
        </a>
      {%- endif -%}
    {%- endfor -%}
  </div>
</div>

方案2：遍历单标签逐个匹配（匹配精度最高） #

遍历当前文章的每一个标签，单独转小写后和目标标签匹配，完全避免部分匹配问题：

{% assign taggs = "T-shirt,bag,Purse,Handbag" | split: "," %}
{%- assign length = b_s.related_article_blog_count | plus: 0 -%}
{% capture fourthtag %}{{ taggs[3] | downcase }}{% endcapture %}
<div class="jj-post-content">
  <div class="item">
    {%- for article in blogs[blog].articles limit: length -%}
      {% assign tag_matched = false %}
      <!-- 遍历当前文章的所有标签 -->
      {% for tag in article.tags %}
        {% if tag | downcase == fourthtag %}
          {% assign tag_matched = true %}
          {% break %}
        {% endif %}
      {% endfor %}
      {% if tag_matched %}
        <a href="{{ article.url }}">
          <div class="jj-title">{{ article.title }}</div>
        </a>
      {%- endif -%}
    {%- endfor -%}
  </div>
</div>

内容的提问来源于stack exchange，提问作者Jetro Olowole