Drupal 8: Content Entities

Content entities are used to store information in database that can be translated and revisioned.

Getting Started

NOTE: Make sure you are working on local git repo, to revert back any unwanted changes, or examining generated codes

  1. Use drupal console to generate some boilerplate code to get things started.

    $ drupal generate:entity:content
  • The console will ask several questions about the new content entity, like: the module this entity belongs to, Label and machine_name.
  • Use console help to find what arguments this command accepts.
  • Revert back all changed files, and remove added one, and repeat the generate:entity:content command using --learning option.
  • Examin generated files and changes and try to guess what they do.
  1. Until drupal v0.9.8 the generated code have some issues solve them:
  • Forms: Find the generated form files and fix them; rename and move them according to their content
  • Routes: Find the two routes that have the same path, change on of them. Make sure that changed path has no other dependency pathes.
  • Links: Use Drupal 8 Config Menu Links wiki to create a new configuration links block at admin/config page, and the links to main entity routes there.
  1. Fields There are two ways to add fields to entities, use both of them to add different fields:
    1. ContentEntityBase::baseFieldDefinitions()
    2. Using Field UI
  2. Field Validation Use Entity Validation API in Drupal 8 to add constraint to field item properties. Try adding the following validations:
    1. Email
    2. Unique
    3. Not Blank!
  3. Interfaces Use the intreface class to add setters and getters for this content type.
  4. Install your entity Schema If your module was already installed, clear the cache. If it wasn’t installed yet, install it now to install the entity database schema. Examin the create database table.
  5. Entity Listing: Try adding few entity instances using the create route to find the form and examin the listing, there is no entity view link in the listing table. Find the listing class and add columns to show one or two extra fields and make the name column links to entity view URL

Entity Challenges

Working with content entity is not a smooth joureny, there are some challenges that you need to be aware of.

  • In Drupal 8 there is no module disable. You can either install or uninstall a modules. You can not uninstall a module with content entity, if the content entity table is not empty, or doesn’t exist. Try it!
  • Content Entity database schema updates implemented at ContentEntityBase::baseFieldDefinitions() are applied on only two events (for now):
    • Cache Rebuild if the module was enabled and you created the entity class
    • Module Install will apply the updates, which means:
    • If there was a problem in the ContentEntityBase::baseFieldDefinitions() method that prevented the entity table from being created, you’ll have to create it first by hand and then you can uninstall your module! Use simple command like $ echo 'CREATE TABLE entity_machine_name (id int);' | drush sqlc
  • Try to add any validation to fields created throught Field UI using only Drupal core, it is not that simple if not impossible for now!
  • Uninstall and re-install your module, where are the attached entities?! Use configuration export to persist them.