Domain-Driven Design - Creating aggregates and enforcing invariants spanning multiple aggregates

Deployment.php

<?php

final class Deployment1
{
    public static function with(DeploymentId $anId, EmploymentContractId $anEmploymentContractId,
                                DeploymentPeriod $aPeriod): Deployment
    {
        // No period range validation, final period was already validated and passed
    }
}

final class Deployment2
{
    public static function with(DeploymentId $anId, EmploymentContractId $anEmploymentContractId,
                                EmploymentPeriod $anEmploymentPeriod, DeploymentPeriod $aPeriod): Deployment
    {
        // Check range of deployment period inside employment period
    }
}

final class Deployment3
{
    public static function with(DeploymentId $anId, EmploymentContractReadModelInterface $anEmploymentContractReadModel,
                                DeploymentPeriod $aPeriod): Deployment
    {
        // Get employment period from read model, then do the check
        // Check range of deployment period inside employment period
        if (!$this->inRange($aPeriod, $anEmploymentContractReadModel->period())) {
            throw new InvalidDeploymentPeriodException();
        }        
        
        return new self($anId, $anEmploymentContractReadModel->id(), $aPeriod);
    }
}

Solution1.php

<?php

final class DeployEmployeeHandler
{
    public function __invoke(DeployeEmployee $command): void
    {
        $contract = $this->contracts->ofId($command->contractId()); // Event-sourced aggregate root WRITE model
        
        $deployment = $contract->deploy($command->deploymentId(), $command->deploymentPeriod());
        
        $this->deployments->add($deployment); // Add to deployment event-stream
    }
}

final class EmploymentContract
{
    /** @var EmploymentContractId */
    private $id;
  
    /** @var EmploymentPeriod */
    private $period;
  
    public function deploy(DeploymentId $anId, DeploymentPeriod $aPeriod): Deployment1
    {
        // Check range of deployment period inside employment period
        if (!$this->inRange($aPeriod, $this->period)) {
            throw new InvalidDeploymentPeriodException();
        }
      
        return Deployment1::with($anId, $this->id, $aPeriod);
    }
}

Solution2.php

<?php

final class DeployEmployeeHandler
{
    public function __invoke(DeployeEmployee $command): void
    {
        $contract = $this->contracts->ofId($command->contractId()); // READ model
        
        $deployment = Deployment2::with(
            $command->deploymentId(), $command->employmentContractId(),
            $contract->employmentPeriod(), $command->deploymentPeriod()
        );
        
        $this->deployments->add($deployment); // Add to deployment event-stream
    }
}

Solution3.php

<?php

final class DeployEmployeeHandler
{
    public function __invoke(DeployeEmployee $command): void
    {
        $contract = $this->contracts->ofId($command->contractId()); // READ model
        
        $deployment = Deployment2::with(
            $command->deploymentId(), $contract, $command->deploymentPeriod()
        );
        
        $this->deployments->add($deployment); // Add to deployment event-stream
    }
}

Please follow the issue here:

• webdevilopers/php-ddd#39