TabRepository.php

<?php

class TabRepository
{
    private $mapping;
    
    public function __construct(/*...*/, TabMapping $mapping)
    {
        $this->mapping = $mapping;
    }
    
    public function findBySlugs($slug, TabType $tabType = null)
    {
        $sql = sprintf('%s WHERE slug = :slug', $this->getSQL($tabType));
        
        // ...
    }
    
    private function getSQL(TabType $tabType = null)
    {
        if ( ! $tabType) {
            $sqlParts = [];
            
            foreach ($this->mapping->getSubclasses() as $discriminatorColumn => $childMapping) {
                $sqlParts[] = sprintf(
                    'SELECT %s, "%s" as type FROM %s', 
                    $childMapping->getColumnList(), 
                    $discriminatorColumn, 
                    $childMapping->getTableName()
                );
            }
            
            return sprintf('SELECT * FROM (%s)', implode(' UNION ALL ', $sqlParts));
        }
        
        $childMapping = $this->mapping->getSubclass($tabType->getSlug());
        
        return sprintf(
            'SELECT %s, "%s" as type FROM %s', 
            $childMapping->getColumnList(), 
            $tabType->getSlug(), 
            $childMapping->getTableName()
        );
    }
}

TabTypeMapping.php

<?php

class TabTypeMapping extends Mapping
{
    public function initialize()
    {
        $this->addColumn('id', 'integer');
        $this->addColumn('name', 'string');
        $this->addColumn('slug', 'string');
    }
}

TabTypeRepository.php

<?php

class TabTypeRepository
{
    private $data = array();
    
    public function __construct(TabTypeFactory $tabTypeFactory)
    {
        $this->tabTypeFactory = $tabTypeFactory;
        
        $this->data = [
            $this->tabTypeFactory->createFromArray([
                'id'   => 1,
                'name' => 'Violão',
                'slug' => 'violao',
            ]),
            // ...
        ];
    }
    
    public function findBySlug($slug)
    {
        foreach ($this->data as $tabType) {
            if ($tabType->getSlug() !== $slug) {
                continue;
            }
            
            return $tabType;
            }
        }
        
        return null;
        }
    }
}