How to limit the display of the `bannerList` tag to only show the first N data in the home page Banner list?

As an experienced website operations expert, I am well aware that how to flexibly control content display is the key to improving user experience and operational efficiency.AnQiCMS provides us with rich customization possibilities with its powerful template tag system.Today, let's delve into a common requirement: how to limit the display of the home page Banner list to only show the first N data items.

Make full use of AnQiCMS template tags, accurately control the number of Banner displays on the homepage

In website operation, the homepage banner area is undoubtedly the key to attracting visitors' attention, conveying core information, and guiding user behavior. The AnQi CMS'sbannerListLabels can conveniently retrieve the Banner image settings from the website backend, making your website full of vitality.However, sometimes we may not want to display all Banners at once, but rather select the first few to achieve a simple page, highlight the key points, or optimize loading speed.

As a senior website operator, I am well aware of the importance of this fine-grained control. Although the template system of Anqi CMS does not directlybannerListprovide in tagslimitIt provides flexible Go language Django template engine syntax, allowing us to limit the number of items displayed on the front end after obtaining the data through clever template tricks.

UnderstandingbannerListThe basic operation of tags

Firstly, let's reviewbannerListThe basic usage of tags. You will usually see similar code in your template file:

{% bannerList banners %}
    {% for item in banners %}
    <a href="{{item.Link}}" target="_blank">
        <img src="{{item.Logo}}" alt="{{item.Alt}}" />
        <h5>{{item.Title}}</h5>
    </a>
    {% endfor %}
{% endbannerList %}

This code will be used tobannerListTags assign all Banner data that meets the conditions (such as, the default group) 【en】type="default"All Banners under it) to assign 【en】bannersthe variable, and then pass throughforProblem is that, 【en】bannersThe variable already contains all Banner data. Therefore, we need toforcrop or limit it during the loop.

Core skill one: useslicefilter to crop data

In AnQiCMS template syntax,sliceA filter is a very practical tool that allows us to extract parts of arrays, slices, or strings, just like the slicing operation in Python.This is the ideal method for limiting the number of banners.

slicethe basic syntax of filters is{{obj|slice:"from:to"}}where,fromis the start index (inclusive),toIs the end index (not included). When we need to get the first N data, it can be omittedfromand use directly":N".

For example, if you want to display only the first 3 Banner data on the homepage, you can modify your template code like this:

{% bannerList banners %}
    {% for item in banners|slice:":3" %} {# 这里使用 slice 过滤器截取前3条数据 #}
    <a href="{{item.Link}}" target="_blank">
        <img src="{{item.Logo}}" alt="{{item.Alt}}" />
        <h5>{{item.Title}}</h5>
    </a>
    {% endfor %}
{% endbannerList %}

Passbanners|slice:":3"we tell the template engine to traverse onlybannersThe first 3 elements (indices 0, 1, 2) in the array.This way, no matter how many banners are set on the backend, the frontend will only display the number you specify.This method is concise and efficient, recommended for priority use.

If you want to make this 'N' value more flexible rather than hard-coded in the template, you can usewithLabel or predefine a variable (if allowed) in the controller. For example, define a variable namedbannerLimita variable:

{% with bannerLimit = 5 %} {# 定义变量 bannerLimit 为 5 #}
    {% bannerList banners %}
        {% for item in banners|slice:":bannerLimit" %} {# 使用变量控制截取数量 #}
        <a href="{{item.Link}}" target="_blank">
            <img src="{{item.Logo}}" alt="{{item.Alt}}" />
            <h5>{{item.Title}}</h5>
        </a>
        {% endfor %}
    {% endbannerList %}
{% endwith %}

Then, you just need to modifybannerLimitBy setting the value, you can easily adjust the display quantity without changing the logic inside the loop.

Core Tip Two: Utilizeforthe loop counter for conditional judgment

Another way to implement it is to useforthe loop's built-inforloop.CounterProperties are conditionally judged.forloop.CounterIt will start from 1 and provide an incrementing number for each iteration. We can combineiftags to control when to stop displaying within the loop.

If you want to display the first 4 Banners, you can write it like this:

{% bannerList banners %}
    {% for item in banners %}
        {% if forloop.Counter <= 4 %} {# 当循环次数小于等于4时才显示 #}
        <a href="{{item.Link}}" target="_blank">
            <img src="{{item.Logo}}" alt="{{item.Alt}}" />
            <h5>{{item.Title}}</h5>
        </a>
        {% endif %}
    {% endfor %}
{% endbannerList %}

The advantage of this method is that the logic is clear and easy to understand. You can also usewithLabels or variables passed from outside to replace hardcoded numbers4to achieve dynamic control. Compared tosliceFilter, this method may perform a few unnecessary loop checks when dealing with a large amount of data, but for scenarios with a limited amount of data like the Banner list, the performance difference is almost negligible.

Actual operation steps

  1. Confirm the target template file:The banner is usually located on the home page of theindex.htmltemplate, or a common header or sidebar fragment, such aspartial/header.html.
  2. FindbannerListTag invocation:Find where you have used it on this file.bannerListThe place of the tag.
  3. Select and apply tips:Choose the one to use based on your preferences and actual needs.sliceFilter orforloop.CounterCondition judgment. Replace the modified code with the original.forLoop part.
  4. Save and test:Save your template file, and refresh the homepage of the website to check if the number of Banner displays meets expectations.

By using the above method, you can easily control the number of banners displayed on the AnQiCMS homepage, which not only helps optimize the page layout and reduce visual burden, but also allows for flexible adjustment of content priority based on operational strategies, thereby enhancing the overall user experience and website conversion rate.

Common Questions (FAQ)

  1. Q: Why?bannerListTags do not have directlimitparameters, butarchiveListwhat tags do?A: This may be a consideration in the design of AnQiCMS.bannerListGenerally used to load a small set of predefined images, it may be considered that filtering at the template level is lighter than adding complex queries at the database level.archiveListThe tag processing is for articles, products, and other large amounts of dynamic content. Limiting the number directly at the database level can significantly improve query efficiency.However, the flexibility of AnQiCMS template engine is enough to allow us to compensate for this through filters or loops.

  2. Q: Can I display the next N data starting from the Mth data instead of the first N?A: Of course. You can useslicethe filter to easily achieve this. The syntax is|slice:"M:M+N"(Please note that the index starts from 0). For example, if you want to display 4 banners starting from the 3rd one (index 2), that is, displaying the 3rd, 4th, 5th, and 6th banners, you can write it like this: banners|slice:"2:6".

  3. Q: What will happen if I set the display quantity N, but the backend actually has fewer than N banners?A: Regardless of which one you usesliceFilter orforloop.CounterCondition judgment, if the actual Banner quantity in the background is less than the N value you set, the template will automatically adapt and only display all available Banners.For example, if you set to display the first 5, but there are only 3 in the background, then only these 3 Banners will be displayed, and no error will be reported or blank areas will appear.