dede field.litpic标签如何正确调用图片？

Of course. Let's break down the dede_field.litpic variable in detail. This is a fundamental concept for anyone working with the DedeCMS (织梦CMS) template engine.

What is dede_field.litpic?

In simple terms, dede_field.litpic is a DedeCMS template variable that holds the URL of the thumbnail or cover image for a specific content article.

Breaking Down the Name

To understand it fully, let's look at its name: dede_field.litpic

• dede_: This is the standard prefix for all DedeCMS template variables. It signifies that this is a system-level variable provided by the DedeCMS engine.
• field: This indicates that the variable is pulling data from a specific field in the database. In DedeCMS, each article's content is stored in a database table (dede_archives), and additional information like thumbnails, authors, etc., are stored in other related tables (dede_arctype, dede_addonarticle, etc.). field tells the system to look at these database fields.
• litpic: This is the specific name of the database field being referenced. litpic is short for "Little Picture". It's the standard field name in DedeCMS used to store the path to an article's thumbnail or cover image.

So, dede_field.litpic translates to: "Get the value from the 'litpic' field for the current article."

How it Works in a Template

This variable is used within DedeCMS template files (usually .htm files) to display the thumbnail image. It's most commonly used in:

• Article list templates (list_article.htm, etc.): To show a small thumbnail next to each article title in a list.
• Article templates (article_article.htm): To display a cover image at the top of the full article page.
• Search results and other dynamic pages.

Basic Usage in HTML:

The most common way to use it is inside an <img> tag.

<img src="{dede_field.litpic}" alt="{dede_field.title}" />

Explanation:

• src="{dede_field.litpic}": The src attribute of the image is set to the value of the litpic field. When the page is loaded, DedeCMS replaces {dede_field.litpic} with the actual image path (e.g., /uploads/230101/1-2301011H302025.jpg).
• alt="{dede_field.title}": It's good practice to use the article's title as the alt text for the image for SEO and accessibility.

The Crucial Context: Where You Use It Matters

The behavior of {dede_field.litpic} can change slightly depending on where it's used in your template. This is because DedeCMS processes different types of pages with different data contexts.

A. Inside an Article List (e.g., list_article.htm)

In a list template, you are usually inside a loop that iterates through many articles. In this context, {dede_field.litpic} refers to the thumbnail of the current article being processed in the loop.

Example from a typical list_article.htm:

{dede:list pagesize='10'}
    <li>
        <!-- This will get the litpic for the article in the current loop iteration -->
        <a href="[field:arcurl/]">
            <img src="{dede_field.litpic}" alt="[field:title]" />
        </a>
        <h2><a href="[field:arcurl/]">[field:title]</a></h2>
        <p>[field:description function='cn_substr(@me,100)']...</p>
    </li>
{/dede:list}

Notice the use of both [field:arcurl/] and {dede_field.litpic}. They are essentially doing the same thing—accessing a field of the current article—but different syntaxes are used in different contexts.

B. Inside a Single Article Page (e.g., article_article.htm)

On the page that displays a single full article, there is no loop. You are viewing one specific article. In this context, {dede_field.litpic} refers to the thumbnail of that single, specific article.

Example from a typical article_article.htm:

<article>
    <!-- This will get the litpic for the single article being viewed -->
    {dede_field.litpic runphp='yes'}
        if(@me != '') {
            @me = '<img src="'.@me.'" alt="{dede:field.title/}" class="cover-image" />';
        } else {
            @me = '<img src="/images/default-cover.jpg" alt="{dede:field.title/}" class="cover-image" />'; // Show a default image if none exists
        }
    {/dede_field.litpic}
    <h1>{dede:field.title/}</h1>
    <div class="info">作者：{dede:field.author/} 日期：{dede:field.pubdate function="MyDate('Y-m-d',@me)"/}</div>
    <div class="content">
        {dede:field.body/}
    </div>
</article>

In this more advanced example, we use runphp='yes' to add conditional logic. This is a very common and powerful pattern:

• if(@me != ''): Checks if the litpic field has a value (i.e., an image was uploaded).
• @me = '...': If it has a value, it wraps the image path in a complete <img> tag.
• else { @me = '...' }: If it's empty, it provides a fallback or default image instead of showing a broken image link.

Important Considerations

A. What if litpic is empty?

If an author didn't upload a thumbnail for an article, the litpic field will be empty. Using <img src="{dede_field.litpic}" /> will result in a broken image link.

Solution: Always use the runphp method shown above to provide a fallback image.

B. Absolute vs. Relative URLs

The litpic field usually stores a relative path (e.g., /uploads/...). This path is relative to your website's root directory. For modern websites, it's often better to use absolute URLs (e.g., https://yourdomain.com/uploads/...) to avoid potential issues.

You can achieve this with the runphp method:

{dede_field.litpic runphp='yes'}
    if(@me != '') {
        // Get the site's root URL from DedeCMS config
        $siteUrl = (defined('cfg_cmspath') ? 'https://'.$_SERVER['HTTP_HOST'] : 'https://yourdomain.com');
        @me = '<img src="'.$siteUrl.@me.'" alt="{dede:field.title/}" />';
    } else {
        @me = ''; // Or a default image
    }
{/dede_field.litpic}

Summary