Plugins

What are plugins?: An overview of how plugins work with the GraphQL schema
Writing a simple plugin: In this tutorial, we add a simple plugin for string fields
Writing a complex plugin: In this tutorial, we'll create a plugin that affects models, queries, and input types

Writing a simple plugin

For this example, we want all String fields to have a truncate argument that will limit the length of the string in the response.

Because it applies to fields, we'll want to implement the FieldPlugin interface for this.

namespace App\GraphQL\Plugin;

use SilverStripe\GraphQL\Schema\Field\Field;
use SilverStripe\GraphQL\Schema\Interfaces\FieldPlugin;
use SilverStripe\GraphQL\Schema\Schema;

class Truncator implements FieldPlugin
{
    public function getIdentifier(): string
    {
        return 'truncate';
    }

    public function apply(Field $field, Schema $schema, array $config = [])
    {
        $field->addArg('truncate', 'Int');
    }
}

Now we've added an argument to any field that uses the truncate plugin. This is good, but it really doesn't save us a whole lot of time. The real value here is that the field will automatically apply the truncation.

For that, we'll need to augment our plugin with some afterware.

namespace App\GraphQL\Plugin;

use SilverStripe\GraphQL\Schema\Field\Field;
use SilverStripe\GraphQL\Schema\Interfaces\FieldPlugin;
use SilverStripe\GraphQL\Schema\Schema;

class Truncator implements FieldPlugin
{
    public function apply(Field $field, Schema $schema, array $config = [])
    {
        // Sanity check
        Schema::invariant(
            $field->getType() === 'String',
            'Field %s is not a string. Cannot truncate.',
            $field->getName()
        );

        $field->addArg('truncate', 'Int');
        $field->addResolverAfterware([static::class, 'truncate']);
    }

    public static function truncate(string $result, array $args): string
    {
        $limit = $args['truncate'] ?? null;
        if ($limit) {
            return substr($result, 0, $limit);
        }

        return $result;
    }
}

Let's register the plugin:

SilverStripe\Core\Injector\Injector:
  SilverStripe\GraphQL\Schema\Registry\PluginRegistry:
    constructor:
      - 'App\GraphQL\Plugin\Truncator'

And now we can apply it to any string field we want:

# app/_graphql/types.yml
Country:
  name:
    type: String
    plugins:
      truncate: true

Plugins#

Writing a simple plugin#

Further reading#

What are plugins?

Writing a simple plugin

Writing a complex plugin

Plugins

Writing a simple plugin

Further reading