Question

In college today we made a simple forum in procedural PHP. My homework is to make it so that it’s in OOP (for comparison), this is where I’m stuck.

In OOP a class should only do one thing, right? So a Topic class should allow a topic to be created, set whether replies are allow, and get its replies…

This is what I got so far,

<?php

abstract class Thread {

    protected $_name;   //thread name
    protected $_text;
    protected $_author;
    protected $_allowReplies = true;
    protected $_replies = array();


    function  __construct($name) 
    {
        $this->setName($name);
    }


    protected function setAuthor(User $author)
    {

    } //edited


    function setAllowReplies($replies)
    {
        if (is_bool($replies)) {
            $this->_allowReplies = $replies;
        }
        else
        {
            return false;
        }
    }

    function  setName($name)
    {
        $this->_name = $name;
    }

    function addReply($reply)
    {
        return $this_replies[] = $reply;
    }

    function  makeThread()      //builds up array of values to add to database
    {
        $values =  array();
        //add to database here
    }
}
?>

What I don’t understand is, do I now have to create a class to add the values to the database and an abstract class to add Authors (using Type hinting .etc), or can I just do it here?

(The above class is incomplete because I got halfway and thought I was doing it wrong)

What I’m basically trying to say is, am I designing the above class correctly?

Answer 1

In OOP a class should only do one thing, right?

Not quite. A class gathers methods and properties that constitute an object. It is perfectly valid for an object of a particular class to be able to do more than just a single task.

What I don’t understand is, do I now have to create a class to add the values to the database and an abstract class to add Authors (using Type hinting .etc), or can I just do it here?

You don’t need an extra class to add a thread or its values to the database (you could, though). Simply offer interfaces (i.e. methods) to the world to add and manipulate a thread.
Take the author as an example:

/*
 * Assigns the thread to the specified author
 * Returns boolean
 */
public function set_author(Author $a)
{
    // Forge you SQL query based on the author $a's data and
    // send it to your database

    // How this is done heavily depends on your table topology
}