How to manually apply constraints to object.

symfony-manual-constraints.php

<?php

// Symfony 4 Manual Constraints.
// $obj is your entity object.

private $validator;

// Class ...

public function __constuct(ValidatorInterface $validator) 
{
    $this->validator = $validator;
}

public function getErrors($obj) 
{
    $input  = [
        'origin'    => $obj->getOrigin(),
        'campaign'  => $obj->getCampaign()
    ];
    
    $constraints = new Collection([
        'origin'    => new NotBlank(),
        'campaign'  => new NotBlank()
    ]);
    
    $violations = $this->validator->validate($input, $constraints);
    $errorMessages = [];
    
    if (count($violations) > 0) {
    
        $accessor = PropertyAccess::createPropertyAccessor();
    
        foreach ($violations as $violation) {
    
            $accessor->setValue($errorMessages,
                $violation->getPropertyPath(),
                $violation->getMessage());
    
        }
    }
    
    return $errorMessages
}

//...