Render Parent Paragraph Depending On Dynamic Data From Child Paragraph (e.g. Db Query)

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Introduction

In Drupal 8, theming and hooks provide a powerful way to customize the rendering of paragraphs. However, when dealing with dynamic data from child paragraphs, such as database queries, the process can become more complex. In this article, we will explore how to render parent paragraphs depending on dynamic data from child paragraphs, using the example of a concert content type and a paragraph type concerts_list.

Problem Statement

Let's assume we have a content type concert, which includes a paragraph type concerts_list. This paragraph displays a list of upcoming concerts (concert nodes) retrieved from a database query. The concerts_list paragraph is referenced in various places on the site, such as the concert's detail page and the homepage. However, when the database query returns no results, the concerts_list paragraph is still rendered, resulting in an empty list.

Solution Overview

To solve this problem, we will use a combination of theming and hooks to conditionally render the concerts_list paragraph based on the dynamic data from the database query. We will create a custom module that provides a hook to preprocess the concerts_list paragraph and a theme function to render the paragraph.

Step 1: Create a Custom Module

First, we need to create a custom module that will provide the necessary functionality. Let's call our module concerts_list.

drush generate module concerts_list

Step 2: Create a Hook to Preprocess the Paragraph

In our custom module, we will create a hook to preprocess the concerts_list paragraph. This hook will be called hook_preprocess_concerts_list.

// concerts_list.module
function concerts_list_preprocess_concerts_list(&$variables) {
  // Get the database query results
  $query = \Drupal::entityQuery('node')
    ->condition('type', 'concert')
    ->condition('status', 1)
    ->sort('field_date', 'ASC')
    ->range(0, 5); // Get the top 5 upcoming concerts
  $results = $query->execute();

// Check if there are any results
if ($results) {
// Set the variable to render the paragraph
$variables['concerts_list'] = $results;
} else {
// Set the variable to not render the paragraph
$variables['concerts_list'] = NULL;
}
}

Step 3: Create a Theme Function to Render the Paragraph

Next, we will create a theme function to render the concerts_list paragraph. This theme function will be called theme_concerts_list.

// concerts_list.theme
function theme_concerts_list($variables) {
  // Check if there are any results
  if ($variables['concerts_list']) {
    // Render the paragraph
    return '<ul>' . implode('', array_map(function ($concert) {
      return '<li>' . $concert->getTitle() . '</li>';
    }, $variables['concerts_list'])) . '</ul>';
  } else {
    // Do not render the paragraph
    return '';
  }
}

Step 4: Use the Theme Function in the Template

Finally, we will use the theme function in the template to render the concerts_list paragraph.

<!-- concerts_list.html.twig -->
{% if concerts_list %}
  <ul>
    {% for concert in concerts_list %}
      <li>{{ concert.title }}</li>
    {% endfor %}
  </ul>
{% endif %}

Conclusion

In this article, we have explored how to render parent paragraphs depending on dynamic data from child paragraphs in Drupal 8. We have created a custom module that provides a hook to preprocess the concerts_list paragraph and a theme function to render the paragraph. We have also used the theme function in the template to render the paragraph. This solution provides a flexible and maintainable way to conditionally render paragraphs based on dynamic data.

Additional Tips and Variations

  • To make the solution more robust, you can add error handling to the database query and the theme function.
  • To make the solution more flexible, you can create a configuration option to control the number of concerts to display.
  • To make the solution more maintainable, you can create a separate module for the theme function and the template.

References

Introduction

In our previous article, we explored how to render parent paragraphs depending on dynamic data from child paragraphs in Drupal 8. In this article, we will answer some frequently asked questions about dynamic paragraph rendering in Drupal 8.

Q: What is the difference between a hook and a theme function?

A: A hook is a function that is called by Drupal to perform a specific task, such as preprocessing a paragraph. A theme function, on the other hand, is a function that is used to render a paragraph.

Q: How do I use a hook to preprocess a paragraph?

A: To use a hook to preprocess a paragraph, you need to create a function that implements the hook and returns the preprocessed data. For example, to preprocess a concerts_list paragraph, you would create a function called hook_preprocess_concerts_list that returns the preprocessed data.

Q: How do I use a theme function to render a paragraph?

A: To use a theme function to render a paragraph, you need to create a function that implements the theme function and returns the rendered HTML. For example, to render a concerts_list paragraph, you would create a function called theme_concerts_list that returns the rendered HTML.

Q: How do I use a template to render a paragraph?

A: To use a template to render a paragraph, you need to create a template file that contains the HTML for the paragraph. For example, to render a concerts_list paragraph, you would create a template file called concerts_list.html.twig that contains the HTML for the paragraph.

Q: How do I conditionally render a paragraph based on dynamic data?

A: To conditionally render a paragraph based on dynamic data, you can use a combination of hooks and theme functions. For example, you can use a hook to preprocess the paragraph and a theme function to render the paragraph based on the preprocessed data.

Q: How do I make my paragraph rendering solution more robust?

A: To make your paragraph rendering solution more robust, you can add error handling to your hook and theme function. For example, you can check for errors in the database query and handle them accordingly.

Q: How do I make my paragraph rendering solution more flexible?

A: To make your paragraph rendering solution more flexible, you can create a configuration option to control the number of paragraphs to display. For example, you can create a configuration option to control the number of concerts to display in the concerts_list paragraph.

Q: How do I make my paragraph rendering solution more maintainable?

A: To make your paragraph rendering solution more maintainable, you can create a separate module for the theme function and the template. For example, you can create a separate module for the concerts_list theme function and the concerts_list template.

Conclusion

In this article, we have answered some frequently asked questions about dynamic paragraph rendering in Drupal 8. We have covered topics such as hooks, theme functions, templates, and conditional rendering. We hope that this article has been helpful in answering questions and providing you with a better understanding of dynamic paragraph rendering in Drupal 8.

Additional Tips and Variations

  • To make your paragraph rendering solution more robust, you can use a try-catch block to catch any errors that may occur during the rendering process.
  • To make your paragraph rendering solution more flexible, you can create a configuration option to control the layout of the paragraph.
  • To make your paragraph rendering solution more maintainable, you can use a separate module for the theme function and the template.

References