Question

In the development of a website, I encountered this problem. I want to pass an object into a class, and afterwards I’d like to use it’s methods. Here’s what I’m trying to do:

[updated code below]

First I create a new theme and header. Then I’d like to use the newly created $theme in my Header class. So I need to pass it. I want to use the same instance of $theme in multiple classes, so I can’t create a new one. Also I’d like to avoid using a Singleton.

With my current code I’m getting this error:

Fatal error: Call to a member function getHeader() on a non-object in...

My questions:

• Is this approach going to work or is it completely wrong?
• How can I pass an object to another object and then still be able to use it’s methods?
• Might it be better to use a singleton instead and use Theme::getInstance(); to use it in the other class?

[edit]
More detailled code:

$theme = new Theme($db);
$builder = new Builder($login, $db, $theme);
$builder->build();

Builder.php:

class Builder {
    private $login;
    private $db;
    private $theme;

    public function __construct($login, $db, $theme){
        $this->login = $login;
        $this->db = $db;
        $this->theme = $theme;
    }

    public function build(){
        $this->buildHeader();
        $this->buildContent();
        $this->buildFooter();
    }

    public function buildHeader(){
        $header = new HeaderBuilder($this->login, $this->db);
        $header->setTheme($this->theme);
        $header->render();
    }

    public function buildContent(){}
    public function buildFooter(){}
}

Abstract builder class:

abstract class AbstractBuilder {
    private $variable = array();
    private $login;
    private $db;
    private $view;

    abstract function build();

    public function __construct($login, $db){
        $this->login = $login;
        $this->db = $db;
        $this->build();
    }

    public function render(){
        extract($this->variable);
        include($this->view);
    }
}

HeaderBuilder:

class HeaderBuilder extends AbstractBuilder {
    private $theme;

    public function build(){
        $this->view = $this->theme->getHeader();
    }

    public function setTheme($theme){
        $this->theme = $theme;
    }       
}

Answer 1

Your approach works fine in the following code:

$theme = new Theme();
$header = new Header();
$header->setTheme($theme);
$header->build();

class Header {
    private $theme;

    public function setTheme($theme){
        $this->theme = $theme;
    }

    public function build(){
        $this->view = $this->theme->getHeader();
    }
}

class Theme {
    public function getHeader() {
        echo 'yes';
    }
}

Perhaps there’s something else that’s stopping it from working?

EDIT

A quick spot, you mistyped construct:

public function __constuct($login, $db, $theme){
    $this->login = $login;
    $this->db = $db;
    $this->theme = $theme;
}

EDIT2 I found your error:

When new HeaderBuilder() gets called:

    $header = new HeaderBuilder($this->login, $this->db);

$this->build(); gets executed in your AbstractBuilder:

public function __construct($login, $db){
    $this->login = $login;
    $this->db = $db;
    $this->build();
}

Which points to

public function build(){
    $this->view = $this->theme->getHeader();
}

In your HeaderBuilder.. BUT! That $this->build(); is being called before the $header->setTheme() is being called, so the $theme variable in HeaderBuilder is empty.
Commenting out that $this->view = … line makes the code work again.