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Database Patterns: DAO/VO

omegaUp uses the DAO/VO (Data Access Object / Value Object) pattern for all database interactions.

Pattern Overview

Value Objects (VO)

  • Map directly to database tables
  • One VO class per table
  • Auto-generated from schema
  • Located in frontend/server/src/DAO/VO/

Data Access Objects (DAO)

  • Static classes for database operations
  • One DAO class per table
  • Methods: search(), getByPK(), save(), delete()
  • Located in frontend/server/src/DAO/

Example Usage

Searching Users

// Create a VO with search criteria
$user = new Users();
$user->setEmail('user@example.com');

// Search using DAO
$results = UsersDAO::search($user);

// Process results
if (count($results) > 0) {
    $foundUser = $results[0];
    echo "User ID: " . $foundUser->getUserId();
    echo "Username: " . $foundUser->getUsername();
}

Creating a Record

// Create new VO
$problem = new Problems();
$problem->setTitle('My Problem');
$problem->setAlias('my-problem');
$problem->setAuthorId($userId);

// Save using DAO
ProblemsDAO::save($problem);

Getting by Primary Key

// Get user by ID
$user = UsersDAO::getByPK($userId);
if ($user !== null) {
    echo $user->getUsername();
}

Key Principles

No Direct SQL in Controllers

Controllers never write SQL directly. They use DAOs:

// ✅ Good: Using DAO
$runs = RunsDAO::searchByUserId($userId);

// ❌ Bad: Direct SQL
$runs = $conn->query("SELECT * FROM Runs WHERE user_id = ...");

Avoid O(n) Queries

Create manual queries for single round trips:

// ❌ Bad: Multiple queries
foreach ($users as $user) {
    $runs = RunsDAO::searchByUserId($user->userId);
}

// ✅ Good: Single query
$userIds = array_map(fn($u) => $u->userId, $users);
$runs = RunsDAO::searchByUserIds($userIds);

Auto-Generation

VO and DAO classes are auto-generated from the database schema:

  1. Modify database schema (add migration)
  2. Run ./stuff/update-dao.sh
  3. VO and DAO classes are regenerated