2.3 KiB
title | summary |
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Writing a simple plugin | In this tutorial, we add a simple plugin for string fields |
Plugins
[CHILDREN asList]
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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 FieldPlugin
for this.
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 implements 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 the resolver with some afterware.
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:
- 'MyProject\Plugins\Truncator'
And now we can apply it to any string field we want:
app/_graphql/types.yml
Country:
name:
type: String
plugins:
truncate: true
Further reading
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