致命错误：不在对象上下文中时使用$ this

Question

I have this class which I wrote for a factory method and I keep getting an error on line 22 which states:

Fatal error: Using $this when not in object context

I have seen other peoples posts and similar questions but alas I don't understand whats going on enough to be able to apply what they took as an answer to my situation.

my class is called as such:

$class = AisisCore_Factory_Pattern('class_you_want');

And then from there the following is executed:

class AisisCore_Factory_Pattern {

    protected static $_class_instance;

    protected static $_dependencies;

    public function get_instance(){
        if(self::$_class_instance == null){
            $_class_instance = new self();
        }

        return self::$_class_instance;
    }

    public function create($class){
        if(empty($class)){
            throw new AisisCore_Exceptions_Exception('Class cannot be empty.');
        }

        if(null === self::$_dependencies){
            $this->_create_dependecies();
        }

        if(!isset(self::$_dependencies['dependencies'][$class])){
            throw new AisisCore_Exceptions_Exception('This class does not exist in the function.php dependecies array!');
        }

        if(isset(self::$_dependencies['dependencies'][$class]['arguments'])){
            $new_class =  new $class(implode(', ', self::$_dependencies['dependencies'][$class]['params']));
            return $new_class;
        }else{
            $new_class = new $class();
            return $new_class;
        }


    }

    private function _create_dependecies(){
        self::$_dependencies = get_template_directory() . '/functions.php';
    }

}

where it freaks out is on:

$this->_create_dependecies();

I'm not sure how that's out of context or how I would properly call it....

Answer 1

You error says you are using $this when you can't, so here is the part:

$this->_create_dependecies();

change it to :

self::_create_dependecies();

Answer 2

So if you are trying to do this as a singleton your get_instance() method needs to be defined statically. further how are you calling create()? I see no reference to that at all. Perhaps create() should be a public static function and then change your $this->_create_dependecies(); to self::_create_dependencies() and add the static keyword to your definition of the create_dependencies method so it would be public static function create_dependencies. Then you put it all together with...

$class = AisisCore_Factory_Pattern::create('class_you_want');

class AisisCore_Factory_Pattern {

  protected static $_class_instance;

  protected static $_dependencies;

  public static function get_instance(){
    if(self::$_class_instance == null){
        $_class_instance = new self();
    }

    return self::$_class_instance;
  }

  public static function create($class){
    if(empty($class)){
        throw new AisisCore_Exceptions_Exception('Class cannot be empty.');
    }

    if(null === self::$_dependencies){
        self::_create_dependecies();
    }

    if(!isset(self::$_dependencies['dependencies'][$class])){
        throw new AisisCore_Exceptions_Exception('This class does not exist in the function.php dependecies array!');
    }

    if(isset(self::$_dependencies['dependencies'][$class]['arguments'])){
        $new_class =  new $class(implode(', ', self::$_dependencies['dependencies'][$class]['params']));
        return $new_class;
    }else{
        $new_class = new $class();
        return $new_class;
    }


}

private static function _create_dependecies(){
    self::$_dependencies = get_template_directory() . '/functions.php';
}

}

and that should do ya. if you really want to access it non statically (yes I know that's not a real word but I like it) you should be saying something like this...

$class = AisisCore_Factory_Pattern::get_instance()->create('class_you_want');
//or...
$class = AisisCore_Factory_Pattern::get_instance();
$newclass = $class->create('class_you_want');

of course in the second example you would remove the static keyword from the create function definition

Answer 3

我相信您应该编写$class = new AisisCore_Factory_Pattern("class_you_Want");