Jekyll 无法在“nil”上使用concat`

我正在尝试为我的Jekyll站点构建一个相关的post include文件。该网站以会员、景点和公园（每一个都是收藏品）的概念为基础。每个帖子都有多对多的关系。我正在尝试建立一个包含每个页面属性（成员、景点和公园）的组合数组，在数组中循环，并查找带有相同数量标签的帖子

这很简单，但是我被一个部分卡住了，不是所有的帖子都有会员、景点和公园字段，所以他们返回

nil

，但是concat过滤器需要一个数组。我试图将变量默认为

[]

，但它总是设置为

nil

。有什么想法吗

代码如下：

<ul class="row">

    {% assign pageTags = [] %}{% if page.tags.first %}{% assign pageTags = page.tags %}{% endif %}
    {% assign pageAttractions = [] %}{% if page.attractions.first %}{% assign pageAttractions = page.attractions %}{% endif %}
    {% assign pageMembers = [] %}{% if page.members.first %}{% assign pageMembers = page.members %}{% endif %}
    {% assign pageParks = [] %}{% if page.parks.first %}{% assign pageParks = page.parks %}{% endif %}
    {% assign pageTagList = pageTags | concat: pageAttractions | concat: pageMembers | concat: pageParks %}

    {% for post in site.documents %}
        {% assign sameTagCount = 0 %}
        {% assign commonTags = '' %}
        {% assign postTags = [] %}{% if post.tags %}{% assign postTags = post.tags %}{% endif %}
        {% assign postAttractions = [] %}{% if post.attractions %}{% assign postAttractions = post.attractions %}{% endif %}
        {% assign postMembers = [] %}{% if post.members %}{% assign postMembers = post.members %}{% endif %}
        {% assign postParks = [] %}{% if post.parks %}{% assign postParks = post.parks %}{% endif %}

        {% assign postTageList =  postTags | concat: postAttractions | concat: postMembers | concat postParks %}

        {% if post.hidden == true %}
            {% break %}
        {% endif %}

        {% for tag in postTageList %}
            {% if post.url != page.url %}
                {% if pageTagList contains tag %}
                    {% assign sameTagCount = sameTagCount | plus: 1 %}
                    {% capture tagmarkup %} <span class="label label-default">{{ tag }}</span> {% endcapture %}
                    {% assign commonTags = commonTags | append: tagmarkup %}
                {% endif %}
            {% endif %}
        {% endfor %}

        {% if sameTagCount >= minCommonTags %}
                <li class="col-lg-4 col-md-12">
                    <div class="main-image">
                        <a href="{{ post.url }}" class="image" style="background-image: url('{{ post.image }}');"></a>
                    </div>
                    <h5>{{ post.categories | first }}</h5>
                    <h3><a href="{{ post.url }}">{{ post.title | replace: 'Review', '' }}</a></h3>
                    <p> 
                        {% if post.description %}
                            {{ post.description }}
                        {% else %}
                            {{ post.content | markdownify | strip_html | truncatewords: 20 }}
                        {% endif %}
                    </p>
                    <p>
                        <a href="{{ post.url }}" class="large">Read Article &rarr;</a>
                    </p>
                </li>
            {% assign maxRelatedCounter = maxRelatedCounter | plus: 1 %}
            {% if maxRelatedCounter >= maxRelated %}
                {% break %}
            {% endif %}
        {% endif %}
    {% endfor %}
    </ul>

{%assign pageTags=[]%}{%if page.tags.first%}{%assign pageTags=page.tags%}{%endif%}
{%assign pageAttractions=[]%}{%if page.attractions.first%}{%assign pageAttractions=page.attractions%}{%endif%}
{%assign pageMembers=[]%}{%if page.members.first%}{%assign pageMembers=page.members%}{%endif%}
{%assign pageParks=[]%}{%if page.parks.first%}{%assign pageParks=page.parks%}{%endif%}
{%assign pageTagList=pageTags | concat:pageAttractions | concat:pageMembers | concat:pageParks%}
{site.documents%中的post为%s}
{%assign sameTagCount=0%}
{%assign commonTags=''%}
{%assign postTags=[]%}{%if post.tags%}{%assign postTags=post.tags%}{%endif%}
{%assign postAttractions=[]%}{%if post.attractions%}{%assign postAttractions=post.attractions%}{%endif%}
{%assign postMembers=[]%}{%if post.members%}{%assign postMembers=post.members%}{%endif%}
{%assign postParks=[]%}{%if post.parks%}{%assign postParks=post.parks%}{%endif%}
{%assign postTageList=postTags | concat:posttractions | concat:postMembers | concat postParks%}
{%if post.hidden==true%}
{%break%}
{%endif%}
{postTageList%中标记的%s}
{%if post.url！=page.url%}
{%如果pageTagList包含标记%}
{%assign sameTagCount=sameTagCount | plus:1%}
{%capture tagmarkup%}{{tag}{%endcapture%}
{%assign commonTags=commonTags | append:tagmarkup%}
{%endif%}
{%endif%}
{%endfor%}
{%if sameTagCount>=minCommonTags%}

{{post.categories | first}}

{%if post.description%}
{{post.description}}
{%else%}
{{post.content | markdownify | strip | html | truncatewords:20}
{%endif%}




{%分配maxRelatedCounter=maxRelatedCounter |加：1%}
{%如果maxRelatedCounter>=maxRelated%}
{%break%}
{%endif%}
{%endif%}
{%endfor%}

---

您可以在这里看到repo:

您应该看看compact，它从数组中删除任何nil值

这是一个关于shopify的文档

液体文档中的示例

输入：

{% assign site_categories = site.pages | map: "category" %}

{% for category in site_categories %}
- {{ category }}
{% endfor %}

{% assign site_categories = site.pages | map: "category" | compact %}

{% for category in site_categories %}
- {{ category }}
{% endfor %}

输出：

- business
- celebrities
-
- lifestyle
- sports
-
- technology

- business
- celebrities
- lifestyle
- sports
- technology

输入：

{% assign site_categories = site.pages | map: "category" %}

{% for category in site_categories %}
- {{ category }}
{% endfor %}

{% assign site_categories = site.pages | map: "category" | compact %}

{% for category in site_categories %}
- {{ category }}
{% endfor %}

输出：

- business
- celebrities
-
- lifestyle
- sports
-
- technology

- business
- celebrities
- lifestyle
- sports
- technology

从：

不能仅使用液体初始化数组

但是，可以使用过滤器将字符串拆分为子字符串数组

---

仅供参考，将空字符串拆分为空字符串：

{%assign pageMembers=”“|split:%}