Is there a pattern similar to Singleton?

Question

It’s really frustrating, a little interesting maybe, but frustrating above all, just yesterday I figured out how and why to use the pattern Singleton, And today, as I was about to finish a little improvement on a project, I saw the true face of the pattern. Let’s just say I’m a little lost at the moment, because I made the system based on that pattern, and that’s about 10 classes, each containing an average of 6~7 methods, not counting the properties. I don’t know the other patterns because I never had a chance to try them out and see how they work, or how far they go.

Let’s say I have this script:

# instancia para retornar todos os valores no banco de dados
$database = Database::getInstance()->get(false,array('nickname','like','',true));

# teste, para a mensagem da sessão
if(Session::exists('sucesso')):
    print Session::pop('sucesso');
    print "<br/>";
endif;

# teste, para a sessão
if(Session::exists(Config::get('session@session_name'))){
    //print Session::get(Config::get('session@session_name')) . "<br/>";
    print Hash::decode(Session::get(Config::get('session@session_name'))) . "<br/>";
}

# teste, para o login
# classe faz o uso de Database::getInstance()
$usuario = new User();
if($usuario->logado()){
    print "Logado";
} else {
    print "Logue primeiro";
}

# Iterar o objecto e imprimir os respectivos valores
if($database){
    print "<p><b>(".$database->count().") Resultados Encontrados</b></p>";
    $campo_s = Config::get('mysql_fetch@campo_s');
    $campo_n = Config::get('mysql_fetch@campo_n');
    foreach($database->results() as $key=>$object){
        print $object->$campo_s . ' - ' . $object->$campo_n. "<br/>";
    }
} else {
    print Database::error();
    print "Consulta não efetuada";
}

# teste, para a hora
print "<p>Data:\r<b>".Config::dateTime()."</b></p>";

Right in the first line of this code script, I have an instance of my connection, and I also passed some parameters to make a query, for now everything is fine.

Somewhere around the middle of script, create a class instance User which perhaps also makes use of the connection class, and sets parameters for an authentication search.

In the loop foreach I was supposed to be able to print all the values corresponding to my first query in the database, but that’s not what happens, I get only 1 single result, which refers to the authenticated user. I soon got to thinking, what I’m doing wrong, after 35~40s I realized it was the pattern I’m currently using, that is, if a base of operation is set right at the top, and suddenly another instruction comes up in the middle, the rest of the block acts according to these instructions, even if it involves rewriting the search.

At bottom it’s just a linear operation, where all the instructions are processed in line, as if it were a thin pipe.

Here’s the pattern, used:

private function __construct(){

}
// Singleton initialization
public static function getInstance(){
    if(is_null(self::$_instance)){
        self::$_instance = new Database();
    }
    return self::$_instance;
    # Desta forma funciona, mas viola o principio do padrão aplicado
    # Procurar possível solução (encontrada).
    /*
    self::$_instance = new Database();
    return self::$_instance;
    */
}

At first I did tests to see if it was really because of the pattern, so I started at the core of this pattern, where I removed the condition responsible for creating unique instances, and I did the following:

self::$_instance = new Database();
return self::$_instance;

I passed the test and it worked, so I had to return the method as it was, because this way I would be violating the pattern, and do "I don’t know what", that somehow had solved my problem.

Then I thought, because they are linear instructions and processed one by one, why not move the first instance to the end of the first block? So that’s what I did.

$database = Database::getInstance()->get(false,array('nickname','like','',true));

I moved this instance to after the first, I did the test and it worked normally.

I can say that at the moment I found no problems in using the pattern in this project, but what I would really like to know is:

What is the pattern with the most resemblance to the Singleton, that allows me to use public methods without prior instance?

Or, what is the alternative method that can be easily implemented in a project in half or almost at the end? Taking into account that it would rewrite only the connection instance in the connection class, keeping the structure in the scripts or Clases that make use of it.

Answer 1

I will not answer anything from the beginning that is not very relevant because it would take a lot of time and deep down you will not want the solution I have, but it is all wrong. It’s not a pattern problem, it’s the lack of it as it was conceived. This would not happen if it had developed in a simple way using techniques that dominates.

There is no similar pattern. Actually the closest is not to use this pattern. Or it uses a totally static class, without needing to create an instance or even the class creates, it does everything "procedural". Or leave it the way it is because the problem is different. This would be the best, since it started to do so. It would be difficult to change without rethinking the whole project.

I think you’ve fallen into the syndrome of Pattern design. Which is very common. You’ve heard so much about the PD that you thought you had to use it somewhere. Can you say any real advantage to your code obtained by using it? Be compared to a static class, or no class at all.

I feel like you just wanted to take a trip and had to learn mechanics and assemble the engine to get what you wanted. Obviously, the first set-ups will go wrong, so when you start putting it together you’ll realize you didn’t have to do this.

Experienced programmers - and not stubborn ones - have learned (or by having made a mistake, or by having read good publications, or by self-perception) that it is easier just to make the trip.