Cross Boundary Example

CrossBoundaryExample.php

<?php

// Example of the Scheduling domain needing data from the User domain.

// ====================
// User Domain
// ====================

// User domain declares an application-level interface other contexts can reference.
// Currently in our app, these would just be the Commands and Queries inside the context.
// --
// The objects returned should only contain data (DTO), and no behaviour.
// --
// User/Application/IUserService.php
interface IUserService {
    public function listUsers(ListUsersQuery $query): User[];
    public function createUser(CreateUserCommand $command): int; // would actually be a handler
}


// ====================
// Scheduling Domain
// ====================

// Scheduling declares it's own representation of a "User" with properties that make sense for scheduling.
// This is a value-object and shouldn't have it's own repository in scheduling.
// --
// Scheduling/Domain/Employee.php
class Employee {
    public $id;
    public $name;
    // etc.
}

// Scheduling domain defines an interface for the data it requires.
// --
// Scheduling/Domain/IEmployeeService.php
interface IEmployeeService {
    public function getEmployees(): Employee[];
}

// Scheduling implements the IEmployeeService within it's infrastructure layer.
// The implementation queries the Scheduling domain, and maps the User data into it's own value object.
// --
// Scheduling/Infrastructure/EmployeeService.php
class EmployeeService implements IEmployeeService {
    /** @var IUserService from User context. */
    private $user_service;

    public function getEmployees(): Employee[] {
        $users = $this->user_service->listUsers(new ListUsersQuery());

        // Eventually this could be:
        // $users = $this->client->get('/api/v2/users');

        return array_map([$this->employee_mapper, 'fromUser'], $users);
    }
}

// Now scheduling services can depend on the new employee service,
// rather than couple to User code directly, or bloat User code with
// logic specific to the scheduling domain.
// --
// Scheduling/Application/SomeSchedulingService.php
class SomeSchedulingService {
    /** @var IEmployeeService */
    private $employee_service;

    public function someSchedulingAction() {
        $employees = $this->employee_service->getEmployees();
        // do something w/ employees
    }
}