Question

I have a question about a ‘modeling, training‘ classes, there are two simple rules which do not fit in my head, and that such training should provide,

in my model, be it ‘CustomersModel, VehicleModel‘ I ‘have’ to have access to the methods of the writer of queries (SQLBuilder), but also have access to the database, which would not set the mapper as the mapper works on the bench, and not the bank over the mapper, so complicated a little by my situation.

Imagine the following:

<?php
   // database access, mapping
   abstract class Mapper { }
   abstract class Model { } 


   interface Connection { } // to recognize it's a database access 
   class MySQL implements Connection { }
   class PgSQL implements Connection { } 

    // SQL Helper, some methods to write a update, insert, delete, select query
   class SQLBuilder { }

   // my custom models
   class Customers extends Model { }

visualizing this structure, the ‘Customers’, already has access to the mapper, in which case I would have a property ‘$_table‘ (among others) in the Customers table to recognize that this model works, but .. I do not have access to the writer of queries, and not to the database, for this, I thought of a method ‘main()‘, where setaria connection to the database, using the ‘setDatabaseConnection ( Connection $connection )‘ but the code would be often repeated, just imagine for N models, all using -> setDatabaseConnectiom, and the entire application uses only one database? ..

My question is basically that, provide access to the database without using setter method in model (Customers, Vehicle), and the writer of queries right away.

Way i wan’t to use is ..

<?php

       // my models
       class Customers extends Model { 

              // method of mapper does'nt implement
              public function getByCity ( $city ) {
                     $query = $this->select()->from($this->_table)->where('city = ?', $city);
                     $resultSet = $this->getConnection()->query( $query );
                     if ( $resultSet->rowCount() > 1 ) {
                            return $resultSet->fetchAll();
                     } else return $resultSet->fetch();
              }

       }

so how can I use the save (), delete (), update () the mapper.
in this case, the getConnection () method would have to get the default connection, and return the class.

Answer 1

There are several way to handle this. You can have a factory class that will instantiate your Model class. Somthing in the line of:

class ModelLoader {

    public function load($name)
    {
        $class = new $name();
        $class->setConnection(/* set connection class */);
        return $name;
    }
}

$loader = new ModelLoader();
$customer = $loader->load('Customer');

Another way can be by setting a default connection to be used when the connection in the model class isn’t set.

interface Connection {}
class MySQL implements Connection {}
class PgSQL implements Connection {}

abstract class Model {

    private $connection = null;

    private static $defaultConnection;

    public function setConnection(Connection $connection = null)
    {
        if ($connection === null) {
            if (!self::$defaultConnection instanceof Connection) {
                throw new Exception('Default connection missing.');
            }
            $connection = self::$defaultConnection;
        }
        $this->connection = $connection;

        return $this;
    }

    public function getConnection()
    {
        if ($this->connection === null) {
            $this->setConnection();
        }
        return $this->connection;
    }

    public static function setDefaultConnection(Connection $connection)
    {
        self::$defaultConnection = $connection;
    }
}

class Customers extends Model { }
class Vehicle extends Model { }


Model::setDefaultConnection(new MySQL);

$customer = new Customers();
$customer->getConnection();

$vehicle = new Vehicle();
$vehicle->setConnection(new PgSQL);

echo '<pre>';
var_dump($customer);
var_dump($vehicle);

// output
object(Customers)#2 (1) {
  ["connection":"Model":private]=>
  object(MySQL)#1 (0) {
  }
}
object(Vehicle)#3 (1) {
  ["connection":"Model":private]=>
  object(PgSQL)#4 (0) {
  }
}

Hope this helps