[SOLVED] OOP organization

[Boo-urns]

I am thinking of having a few classes for different sections / events for a site. First off I have extended mysqli class. Now where I am confused is I have a class for validation (passwords, zipcodes...etc) Is it best to have a db connection there as well or is there a better way of doing that?

 

Thanks!

[flyhoney]

I dont think its too unreasonable for the Validation class to create its own Database() object

[trq]

Why would a validation class need a database connection?

[Boo-urns]

Validate user logins, or should that be under a User class? What do you suggest?

[genericnumber1]

One simple possible consideration you may have is to implement a database interaction object as a singleton and retrieve the object when it is needed. Unfortunately that also leads to a global connection that can be fairly limiting when implementing your other classes. What I prefer to do is instead of using a singleton or, as suggested before, creating a new database object inside of the class, is to use dependency injection and pass the class a data object when the class is instantiated (edit: or when specific methods are invoked). This allows for more flexible testing of the class and more flexible types of data sources without having to manipulate global data and further interfering with the tested object's encapsulation.

[premiso]

One simple possible consideration you may have is to implement a database interaction object as a singleton and retrieve the object when it is needed. Unfortunately that also leads to a global connection that can be fairly limiting when implementing your other classes. What I prefer to do is instead of using a singleton or, as suggested before, creating a new database object inside of the class, is to use dependency injection and pass the class a data object when the class is instantiated (edit: or when specific methods are invoked). This allows for more flexible testing of the class and more flexible types of data sources without having to manipulate global data and further interfering with the tested object's encapsulation.

 

I am not sure of this in PHP5, but I had that setup in my scripts in PHP4 and it was amazing at how much slower the script ran by passing in the objects. I actually had a "Main" method where I would instantiate an object/return it if called, so only one instance of the object was created, but for whatever reason it slowed it down a ton. Since, this was for PHP4, I created functions, it would still only instantiate the class on a first call, but allowed for that to be used throughout any class, and it worked well.

 

As far as this on PHP5, I have no clue of the side-effects.

 

Just thought I would share my PHP4 experience with that scenario of including the class with the constructor or parameter.

[genericnumber1]

With PHP4 objects were passed by value by default, you had to specifically tell them to pass by reference. So sorry if this is a stupid question, but were you being sure to pass them by reference?

[Boo-urns]

genericnumber1 - can you somewhat describe dependency injection?

 

I've found an example but I'm having problems creating it to work. I'm getting an error: "Fatal error: Call to undefined method BookReader::getChapers()" Which i imagine is the DI not working.

 

<?php
interface Db {
  public function executeSql($sql);
}

class MySqlDb implements Db {
  public function __construct($username, $password, $host) {
    // i took out the constructor and used the mysqli constructor
  }
  public function executeSql($sql) {
    // return something here nothing new...
  }
}

class BookReader {
  private $_db;
  public function __construct(Db $db) {
    $this->_db = $db;
  }
  public function getChapters() {
    return $this->_db->executeSql('SELECT name FROM chapter');
  }
}

$book = new BookReader(new MySqlDb(DB_USER, DB_PASS, DB_HOST));
$chapters = $book->getChapers();

 

Instead of using an interface i just extended the mysqli class for MySqlDb. I just can't wrap my head around this yet :-/

 

[genericnumber1]

getChapters() you missed a 't'

[Boo-urns]

Wow what an embarrassment :-/ thanks for spotting it