--- /dev/null
+<?php
+
+namespace Drupal\{{ machine_name }}\Plugin\Validation\Constraint;
+
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Validates the {{ plugin_label }} constraint.
+ */
+class {{ class }}Validator extends ConstraintValidator {
+
+ /**
+ * {@inheritdoc}
+ */
+{% if input_type == 'entity' %}
+ public function validate($entity, Constraint $constraint) {
+
+ // @DCG Validate the entity here.
+ if ($entity->label() == 'foo') {
+ $this->context->buildViolation($constraint->errorMessage)
+ // @DCG The path depends on entity type. It can be title, name, etc.
+ ->atPath('title')
+ ->addViolation();
+ }
+
+ }
+{% elseif input_type == 'item_list' %}
+ public function validate($items, Constraint $constraint) {
+
+ foreach ($items as $delta => $item) {
+ // @DCG Validate the item here.
+ if ($item->value == 'foo') {
+ $this->context->buildViolation($constraint->errorMessage)
+ ->atPath($delta)
+ ->addViolation();
+ }
+ }
+
+ }
+{% elseif input_type == 'item' %}
+ public function validate($item, Constraint $constraint) {
+
+ $value = $item->getValue()['value'];
+ // @DCG Validate the value here.
+ if ($value == 'foo') {
+ $this->context->addViolation($constraint->errorMessage);
+ }
+
+ }
+{% else %}
+ public function validate($value, Constraint $constraint) {
+
+ // @DCG Validate the value here.
+ if ($value == 'foo') {
+ $this->context->addViolation($constraint->errorMessage);
+ }
+
+ }
+{% endif %}
+
+}