Question

I have the following PHP code as chain of resposibility, I am using PHP5.4.9.

abstract class Logger
{
  protected $next;

  public function next($next)
  {
    $this->next = $next;
    return $this->next;
  }

  public function run(){
    $this->invoke();
    if(null!=$this->next){
      $this->next->invoke();
    }
  }
  abstract public function invoke();
}

class EmailLogger extends Logger
{
  public function invoke()
  {
    print_r("email\n");
  }
}

class DatabaseLogger extends Logger
{
  public function invoke()
  {
    print_r("database\n");
  }
}

class FileLogger extends Logger
{
  public function invoke()
  {
    print_r("file \n");
  }
}

$logger = new EmailLogger();
$logger->next(new DatabaseLogger())->next(new FileLogger());
$logger->run();

the expect output is:

email
database
file

but the actually output:

email
database

I hope to implement chain of resposibility design pattern by PHP language, one abstract class and three or more classes to do something as a chain. but only the first two object works.

Anyting missing? Or PHP can not use this coding style under PHP5.4.9?

Thanks.

Answer 1

Replace

public function run() {
    $this->invoke ();
    if (null != $this->next) {
        $this->next->invoke();
    }
}  

With

  public function run() {
    $this->invoke ();
    if (null != $this->next) {
        $this->next->run ();
    }
}

please try $this->next->invoke() change $this->next->run()