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# Taking Advantage of Column Aggregation Inheritance

First, let me give a brief explanation of what column aggregation inheritance is and how it works. With column aggregation inheritance all classes share the same table, and all columns must exist in the parent. Doctrine is able to know which class each row in the database belongs to by automatically setting a "type" column so that Doctrine can cast the correct class when hydrating data from the database. Even if you query the top level column aggregation class, the collection will return instances of the class that each row belongs to.

Now that you have a basic understand of column aggregation inheritance lets put it to use. In this example we will setup some models which will allow us to use one address table for storing all of our addresses across the entire application. Any record will be able to have multiple addresses, and all the information will be stored in one table. First lets define our Address

> class Address extends Doctrine_Record { public function

setTableDefinition() { $this->hasColumn('address1', 'string', 255); $this->hasColumn('address2', 'string', 255); $this->hasColumn('address3', 'string', 255); $this->hasColumn('city', 'string', 255); $this->hasColumn('state', 'string', 2); $this->hasColumn('zipcode', 'string', 15); $this->hasColumn('type', 'string', 255); $this->hasColumn('record_id', 'integer');

        $this->option('export', 'tables');

        $this->setSubClasses(array('UserAddress'    => array('type' => 'UserAddress'),
                                   'CompanyAddress' => array('type' => 'CompanyAddress')));
    }

}

Note the option set above to only export tables because we do not want to export any foreign key constraints since record_id is going to relate to many different records.

We are going to setup a User so it can have multiple addresses, so we will need to setup a UserAddress child class that User can relate to.

> class UserAddress extends Address { public function setUp() {

$this->hasOne('User', array('local' => 'record_id', 'foreign' => 'id')); } }

Now lets define our User and link it to the UserAddress model so it can have multiple addresses. class User extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('username', 'string', 255); $this->hasColumn('password', 'string', 255); }

    public function setUp()
    {
        $this->hasMany('UserAddress as Addresses', array('local'    => 'id',
                                                         'foreign'  => 'record_id'));
    }

}

Now say we have a Company record which also needs ot have many addresses. First we need to setup the CompanyAddress child class

> class CompanyAddress extends Address { public function setUp() {

$this->hasOne('Company', array('local' => 'record_id', 'foreign' => 'id')); } }

Now lets define our Company and link it to the CompanyAddress model so it can have multiple addresses. class Company extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('name', 'string', 255); }

    public function setUp()
    {
        $this->hasMany('CompanyAddress as Addresses', array('local'    => 'id',
                                                            'foreign'  => 'record_id'));
    }

}

Now both Users and Companies can have multiple addresses and the data is all stored in one address table.

Now lets create the tables and insert some records

> Doctrine_Core::createTablesFromArray(array('User', 'Company',

'Address'));

$user = new User(); $user->username = 'jwage'; $user->password = 'changeme'; $user->Addresses[0]->address1 = '123 Road Dr.'; $user->Addresses[0]->city = 'Nashville'; $user->Addresses[0]->state = 'TN'; $user->save();

$company = new Company(); $company->name = 'centre{source}'; $company->Addresses[0]->address1 = '123 Road Dr.'; $company->Addresses[0]->city = 'Nashville'; $company->Addresses[0]->state = 'TN'; $company->save();

Query for the user and its addresses

> $users = Doctrine_Query::create() ->from('User u')

->leftJoin('u.Addresses a') ->execute();

echo $users[0]->username; // jwage echo `users[0]->Addresses[0]->address1 = '123 Road Dr.'; echo get_class(`users[0]->Addresses[0]);// UserAddress

Query for the company and its addresses

> $companies = Doctrine_Query::create() ->from('Company c')

->leftJoin('c.Addresses a') ->execute();

echo $companies[0]->name; // centre{source} echo `companies[0]->Addresses[0]->address1 = '123 Road Dr.'; echo get_class(`companies[0]->Addresses[0]);// CompanyAddress

Now lets query the Addresses directly and you will notice each child record returned is hydrated as the appropriate child class that created the record initially.

`addresses = Doctrine_Query::create() ->from('Address a') ->execute(); echo get_class(`addresses[0]);// UserAddress echo get_class($addresses[1]); // CompanyAddress