Block API

Information about the classes and interfaces that make up the Block API.

Blocks are a combination of a configuration entity and a plugin. The configuration entity stores placement information (theme, region, weight) and any other configuration that is specific to the block. The block plugin does the work of rendering the block's content for display.

To define a block in a module you need to:

• Define a Block plugin by creating a new class that implements the \Drupal\Core\Block\BlockPluginInterface, in namespace Plugin\Block under your module namespace. For more information about creating plugins, see the Plugin API topic.
• Usually you will want to extend the \Drupal\Core\Block\BlockBase class, which provides a common configuration form and utility methods for getting and setting configuration in the block configuration entity.
• Block plugins use the annotations defined by \Drupal\Core\Block\Annotation\Block. See the Annotations topic for more information about annotations.

The Block API also makes use of Condition plugins, for conditional block placement. Condition plugins have interface \Drupal\Core\Condition\ConditionInterface, base class \Drupal\Core\Condition\ConditionPluginBase, and go in plugin namespace Plugin\Condition. Again, see the Plugin API and Annotations topics for details of how to create a plugin class and annotate it.

There are also several block-related hooks, which allow you to affect the content and access permissions for blocks:

• hook_block_view_alter()
• hook_block_view_BASE_BLOCK_ID_alter()
• hook_block_access()

Further information and examples:

• \Drupal\system\Plugin\Block\SystemPoweredByBlock provides a simple example of defining a block.
• \Drupal\user\Plugin\Condition\UserRole is a straightforward example of a block placement condition plugin.
• \Drupal\book\Plugin\Block\BookNavigationBlock is an example of a block with a custom configuration form.
• For a more in-depth discussion of the Block API, see https://www.drupal.org/developing/api/8/block_api.
• The Examples for Developers project also provides a Block example in https://www.drupal.org/project/examples.

File

core/modules/block/block.api.php, line 10

Hooks provided by the Block module.

Functions

Name	Location	Description
hook_block_access	core/modules/block/block.api.php	Control access to a block instance.
hook_block_build_alter	core/modules/block/block.api.php	Alter the result of \Drupal\Core\Block\BlockBase::build().
hook_block_build_BASE_BLOCK_ID_alter	core/modules/block/block.api.php	Provide a block plugin specific block_build alteration.
hook_block_view_alter	core/modules/block/block.api.php	Alter the result of \Drupal\Core\Block\BlockBase::build().
hook_block_view_BASE_BLOCK_ID_alter	core/modules/block/block.api.php	Provide a block plugin specific block_view alteration.

Classes

Name	Location	Description
Block	core/lib/Drupal/Core/Block/Annotation/Block.php	Defines a Block annotation object.
BlockBase	core/lib/Drupal/Core/Block/BlockBase.php	Defines a base block implementation that most blocks plugins will extend.

Interfaces

Name	Location	Description
BlockPluginInterface	core/lib/Drupal/Core/Block/BlockPluginInterface.php	Defines the required interface for all block plugins.
MainContentBlockPluginInterface	core/lib/Drupal/Core/Block/MainContentBlockPluginInterface.php	The interface for "main page content" blocks.
MessagesBlockPluginInterface	core/lib/Drupal/Core/Block/MessagesBlockPluginInterface.php	The interface for "messages" (#type => status_messages) blocks.
TitleBlockPluginInterface	core/lib/Drupal/Core/Block/TitleBlockPluginInterface.php	The interface for "title" blocks.