用PHP设计噩梦

Question

I've been trying for a long time now to find a correct design using PHP to achieve what I want, but everything I've tried failed and I'm guessing it's probably because I'm not looking from the right angle, so I wish some of you can enlighten me and give me some good advice!

The design might seem a little weird at first, but I assure you it's not because I like to make things complicated. For the sake of simplicity I'm only giving the minimal structure of my problem and not the actual code. It starts with these:

<?php

// ------------------------------------------------------------------------

class Mother_A
{
    const _override_1 = 'default';
    protected static $_override_2 = array();

    public static function method_a()
    {
        $c = get_called_class();
        // Uses $c::_override_1 and $c::$_override_2
    }
}

// ------------------------------------------------------------------------

class Mother_B extends Mother_A
{
    public function method_b()
    {
        // Uses self::method_a()
    }
}

Class Mother_A defines a static method that uses constants and statics to be overridden by children. This allows to define a generic method (equivalent of a "template" method) in the derived class Mother_B. Neither Mother_A or Mother_B are intended to be instanciated, but Mother_B should not be abstract. This exploits Late Static Binding, which I find very useful btw.

Now comes my problem. I want to define two classes, in n distinct 'situations' (situation 1, situation 2, etc):

<?php 

// ------------------------------------------------------------------------

class Child_A_Situation_k extends Mother_A
{
    // Uses method_a
}

// ------------------------------------------------------------------------

class Child_B_Situation_k extends Mother_B
{
    // Uses method_a and method_b
}

Of course I'm not actually giving these stupid names; both classes have different names in each situation, but both follow the same derivation pattern from Mother_A and Mother_B. However, in each individual case ('situation'), both classes need the exact same constants/static override, and I don't know how to do that without duplicating the override manually in both classes.

---

I tried many things, but the closest I got was to implement an interface Interface_Situation_k that defined constants and statics for the situation k, and make both children implement this interface. Of course, you can't define statics in an interface, so it failed, but you get the idea. I would have traded the interface for a class, but then there's no multiple inheritance in PHP, so it's not valid either. :/ I'm really stuck, and I can't wait to read a possible solution! Thanks in advance!

Answer 1

this is the best i can do, i don't think there is a way to do it with less code. Look at the comments inside the code for more info.

Fully working code:

<?php

class Mother_A
{
    // you're using '_override_1' as a variable, so its obviously not a constant
    // also i made it public for the setSituation function, 
    // you could keep it protected and use reflections to set it
    // but i dont really see a reason for that. 
    // if you want that, look up how to set private/protected variables
    public static $_override_1 = 'default'; 
    public static $_override_2 = array();

    public static function method_a()
    {
        $c = get_called_class();
        var_dump($c::$_override_1);
        var_dump($c::$_override_2);
        // Uses $c::_override_1 and $c::$_override_2
    }

    public static function setSituation($className)
    {
        $c = get_called_class();
        // iterate through the static properties of $className and $c 
        // and when the you find properties with the same name, set them
        $rBase = new ReflectionClass($c);
        $rSituation = new ReflectionClass($className);
        $staBase = $rBase->getStaticProperties();
        $staSituation = $rSituation->getStaticProperties();
        foreach($staSituation as $name => $value)
        {
            if(isset($staBase[$name])) $c::$$name = $value;
        }
    }
}

// ------------------------------------------------------------------------

class Mother_B extends Mother_A
{
    public function method_b()
    {
        self::method_a();
    }
}

class Situation_k
{
    public static $_override_1 = 'k';
    public static $_override_2 = array('k','k');
}

class Child_A_Situation_k extends Mother_A { }
Child_A_Situation_k::setSituation('Situation_k'); 
// This is not as short as writing 'extends Mother_A, Situation_k'
// but i think you wont get it shorter

class Child_B_Situation_k extends Mother_B { }
Child_B_Situation_k::setSituation('Situation_k');

echo '<pre>';
Child_A_Situation_k::method_a();
echo "
";
Child_B_Situation_k::method_a();
echo "
";
Child_B_Situation_k::method_b();
echo "
";
echo '</pre>';
?>