Mastering Hook_views_pre_render Getting The Current Display Of A ViewExecutable

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Hey guys! Ever found yourself scratching your head, wondering how to snag the current display ID within hook_views_pre_render? It's a common head-scratcher, but fear not! This article is your ultimate guide to unraveling this mystery. We're diving deep into the intricacies of Drupal's Views API, specifically focusing on how to effectively use hook_views_pre_render to get the current display of a ViewExecutable. So, buckle up and let's get started on this exciting journey!

Understanding the Basics of hook_views_pre_render

First things first, let's break down what hook_views_pre_render actually does. This hook is a crucial part of Drupal's Views module, allowing developers to modify a view before it's rendered. Think of it as your last chance to tweak things before the view is displayed to the user. It's like the final brushstroke on a painting, giving you the power to make those crucial adjustments.

When a view is about to be rendered, Drupal invokes this hook, passing in the \Drupal\views\ViewExecutable object. This object is a treasure trove of information about the view, including its settings, displays, and the data it will render. The main goal here is to tap into this object and extract the display ID, which tells us which display (e.g., 'page_1', 'block_2') is currently being processed. Knowing the display ID is super important because it allows you to apply specific logic or modifications to different displays within the same view.

To get started, you'll need to implement this hook in your custom module. The basic structure looks something like this:


use Drupal\views\ViewExecutable;



/**

 * Implements hook_views_pre_render().

 */

function my_module_views_pre_render(ViewExecutable $view) {

  // Your code goes here

}

In this snippet, my_module should be replaced with the actual name of your module. The ViewExecutable object, passed as $view, is your gateway to all the view's information. Now, let's dive into how to extract that elusive display ID.

Diving Deep: Accessing the Display ID

Now that we've got the basics down, let's get to the heart of the matter: how do you actually get the current display ID? The ViewExecutable object has a method called getDisplay() which returns the DisplayPluginBase object representing the current display. From there, you can call the display_handler to get the display's properties, including the display ID.

Here’s the code snippet that does the magic:


use Drupal\views\ViewExecutable;



/**

 * Implements hook_views_pre_render().

 */

function my_module_views_pre_render(ViewExecutable $view) {

  if ($view->storage->id() == 'your_view_name') {

    $display = $view->getDisplay();

    if ($display) {

      $display_id = $display->display_handler->display['display_options']['id'];

      

      // Do something with $display_id

      

      

    }

  }

}

Let's break this down step by step:

  1. Check the View ID: We first check if the view ID matches the one we're interested in. This is crucial because hook_views_pre_render is called for every view, so you want to make sure your code only runs for the specific view you're targeting. Replace 'your_view_name' with the actual ID of your view.
  2. Get the Display: We then call $view->getDisplay() to get the DisplayPluginBase object for the current display.
  3. Extract the Display ID: The golden nugget! We access the display ID through $display->display_handler->display['display_options']['id']. This might look a bit convoluted, but it's the path to the treasure. It digs into the display's properties and pulls out the 'id', which is the display ID you're after.
  4. Do Something with It: Now that you have the $display_id, you can do whatever you need with it! This might include altering the view's query, changing its title, or modifying the rendered output. The possibilities are endless!

Practical Examples and Use Cases

Okay, so we know how to get the display ID, but let's talk about why you'd want to. There are tons of practical applications for this, so let's explore a few.

Modifying a View Based on the Display

One common use case is to modify a view's behavior based on the display being rendered. For instance, you might want to show different fields or apply different filters depending on whether the view is being displayed as a page or a block.

Here’s an example of how you might do this:


use Drupal\views\ViewExecutable;



/**

 * Implements hook_views_pre_render().

 */

function my_module_views_pre_render(ViewExecutable $view) {

  if ($view->storage->id() == 'your_view_name') {

    $display = $view->getDisplay();

    if ($display) {

      $display_id = $display->display_handler->display['display_options']['id'];

      if ($display_id == 'page_1') {

        // Modify the view for the 'page_1' display

        $view->addFilter('field_your_field', '!=', 'your_value');

      } elseif ($display_id == 'block_1') {

        // Modify the view for the 'block_1' display

        $view->setItemsToDisplay(5); //set the number of items to display

      }

    }

  }

}

In this example, we're checking the $display_id and, based on its value, we're applying different modifications to the view. If the display is 'page_1', we're adding a filter to exclude certain content. If it's 'block_1', we're limiting the number of items displayed. This gives you fine-grained control over how your view behaves in different contexts.

Changing the View Title Dynamically

Another cool use case is changing the view's title dynamically based on the display. This can be useful for providing context-specific titles that make sense to the user.

Here’s how you might do it:


use Drupal\views\ViewExecutable;



/**

 * Implements hook_views_pre_render().

 */

function my_module_views_pre_render(ViewExecutable $view) {

  if ($view->storage->id() == 'your_view_name') {

    $display = $view->getDisplay();

    if ($display) {

      $display_id = $display->display_handler->display['display_options']['id'];

      if ($display_id == 'page_1') {

        $view->setTitle('Page View Title');

      } elseif ($display_id == 'block_1') {

        $view->setTitle('Block View Title');

      }

    }

  }

}

Here, we're setting different titles for the 'page_1' and 'block_1' displays. This can help users understand where the view is being displayed and what content they can expect.

Altering the Query

Sometimes, you might need to alter the view's query based on the display. This could involve adding additional joins, changing the sort order, or applying more complex filters.

Here’s a snippet that shows how to add a join based on the display:


use Drupal\views\ViewExecutable;

use Drupal\views\Plugin\views\query\QueryPluginBase;



/**

 * Implements hook_views_pre_render().

 */

function my_module_views_pre_render(ViewExecutable $view) {

  if ($view->storage->id() == 'your_view_name') {

    $display = $view->getDisplay();

    if ($display) {

      $display_id = $display->display_handler->display['display_options']['id'];

      if ($display_id == 'page_1') {

        /** @var QueryPluginBase $query */

        $query = $view->getQuery();

        $query->addLeftJoin('node_field_data', 'nfd', 'node.nid = nfd.nid', [

          'nfd.type' => 'your_content_type',

        ]);

      }

    }

  }

}

In this example, we're adding a left join to the query if the display is 'page_1'. This allows you to pull in additional data from other tables, giving you more flexibility in what you display in your view.

Best Practices and Common Pitfalls

Before we wrap up, let's touch on some best practices and common pitfalls to avoid when working with hook_views_pre_render.

Performance Considerations

hook_views_pre_render is a powerful tool, but it's important to use it wisely. Since it's called for every view, poorly written code can have a significant impact on performance. Here are some tips to keep in mind:

  • Check the View ID: Always check the view ID at the beginning of your hook implementation. This ensures that your code only runs for the views you're targeting, minimizing overhead.
  • Keep It Lean: Avoid performing complex operations within the hook. If you need to do heavy lifting, consider using caching or other optimization techniques.
  • Limit Database Queries: Be mindful of the number of database queries you're adding. Each query adds to the overall execution time, so try to minimize them as much as possible.

Debugging Tips

Debugging Views hooks can sometimes be tricky, but here are a few tips that can help:

  • Use kint() or dump(): These functions are your best friends for inspecting variables and objects. Use them to check the value of $view, $display, and $display_id at various points in your code.
  • Enable Devel Module: The Devel module provides a wealth of debugging tools, including the ability to display queries and other useful information.
  • Check the Logs: Drupal's logging system can provide valuable insights into errors and warnings. Be sure to check the logs if you're encountering unexpected behavior.

Common Mistakes to Avoid

  • Forgetting to Check the View ID: As mentioned earlier, this is a crucial step. Forgetting to check the view ID can lead to your code running unnecessarily for other views, impacting performance.
  • Modifying the View Too Late: hook_views_pre_render is called before the view is rendered, but after the query has been built. If you need to make changes to the query, make sure you do it within this hook, not later in the rendering process.
  • Overcomplicating Things: Keep your code as simple and straightforward as possible. Overly complex code is harder to maintain and debug.

Conclusion

So, there you have it! You've now mastered the art of getting the current display ID in hook_views_pre_render. With this knowledge, you can create highly customized and dynamic views that adapt to different contexts. Remember to always check the view ID, keep your code lean, and debug effectively. Now go forth and build some awesome views!

By understanding how to tap into the ViewExecutable object and extract the display ID, you're well-equipped to create more flexible and context-aware views. Whether you're modifying the view's behavior, changing its title, or altering the query, the possibilities are endless. Happy coding, guys!