dede getfieldvaluea如何正确使用？

Of course! Let's break down GetFieldValue in the context of DedeCMS (织梦CMS).

What is GetFieldValue?

GetFieldValue is a core PHP function in DedeCMS used to retrieve the value of a single, custom field from an article or other content item.

Think of it this way:

• An article in DedeCMS has standard fields like title, description, body, etc.
• You can add your own custom fields to an article's model (e.g., author_photo, related_download_link, video_url, product_price).
• GetFieldValue is the specific tool you use to fetch the value of just one of those custom fields in your template files (.htm).

The Function Signature

The function is typically called in two ways:

The Static Method (Most Common)

This is the standard way to call it within a DedeCMS template.

<?php
echo GetFieldValue($arcRow, 'field_name');
?>

The Object-Oriented Method

This is an alternative syntax that works in the same way.

<?php
echo $arcRow->GetFieldValue('field_name');
?>

Parameter Breakdown

Let's look at the parameters for the static method: GetFieldValue($arcRow, 'field_name', $isadd, $innertext)

How to Use It: A Step-by-Step Example

Let's say you have an article model with a custom field called video_url.

Step 1: Ensure the Custom Field Exists

1. Log in to your DedeCMS admin panel.
2. Go to "Content" -> "Model Management" -> "Content Model".
3. Click on "Add a new field" for your desired model (e.g., the default article model).
4. Fill in the details:
   • Field Name: video_url (This must be unique and lowercase).
   • Field Type: text or textarea.
   • Fill in other details like title, description, etc.
5. Save the model.

Step 2: Add Data to the Field

1. Go to "Content" -> "Add Article".
2. Fill in the article's title and body.
3. Scroll down to the "Custom Document Fields" section.
4. You will now see a field named video_url. Enter a value for it, for example: https://www.youtube.com/watch?v=dQw4w9WgXcQ.

Step 3: Use GetFieldValue in the Template

Now, you want to display this video URL on your article detail page (article_article.htm).

Open your article_article.htm template file. You will need to find the loop that outputs the article's data. In DedeCMS, this is often an embedded PHP block.

<h1>{dede:field.title/}</h1>
<div class="content">
    {dede:field.body/}
</div>
<!-- Now, let's add our custom field -->
<div class="video-section">
    <h3>Related Video</h3>
    <?php
    // $arcRow is the variable holding the article's data in this context.
    // 'video_url' is the name of our custom field.
    $videoUrl = GetFieldValue($arcRow, 'video_url');
    if (!empty($videoUrl)) {
        echo '<iframe src="' . $videoUrl . '" width="560" height="315" frameborder="0" allowfullscreen></iframe>';
    } else {
        echo '<p>No video available for this article.</p>';
    }
    ?>
</div>

Explanation:

• <?php ... ?>: This is where we write PHP code.
• $videoUrl = GetFieldValue($arcRow, 'video_url');: This line calls the function, gets the value of the video_url field from the current article ($arcRow), and stores it in the $videoUrl variable.
• if (!empty($videoUrl)): This is good practice. It checks if the field has a value before trying to display it, preventing empty <iframe> tags from showing up.
• echo '...': This prints the HTML for the video player if the URL exists.

Important Considerations & Best Practices

1. Case Sensitivity: The 'field_name' parameter is case-sensitive. If your field is named MyField, you must use GetFieldValue($arcRow, 'MyField'). Using 'myfield' will return nothing.
2. Variable Name ($arcRow): The name of the variable holding the article data can change depending on the context.
   • In article detail pages (article_article.htm), it's almost always $arcRow.
   • In arclist loops, it's usually $fields or $row. So you would use GetFieldValue($fields, 'field_name').
3. Check for Emptiness: Always check if a field has a value before using it to avoid errors or broken HTML.
4. Performance: GetFieldValue is very efficient. It only queries the database for the specific field you request, which is faster than retrieving all custom fields if you only need one.

GetFieldValue vs. GetFields

You might also see GetFields. It's important to know the difference:

Example of GetFields:

<?php
// Get all custom fields as an array
$allCustomFields = GetFields($arcRow);
// Now you can loop through them
if (!empty($allCustomFields)) {
    echo '<h3>Additional Information:</h3>';
    echo '<ul>';
    foreach ($allCustomFields as $fieldName => $fieldValue) {
        // You might want to exclude certain fields or format them
        if ($fieldName != 'typeid' && !empty($fieldValue)) {
            echo '<li><strong>' . $fieldName . ':</strong> ' . $fieldValue . '</li>';
        }
    }
    echo '</ul>';
}
?>

In summary, GetFieldValue is your go-to function for cleanly and efficiently retrieving a single custom field's value in a DedeCMS template.