Class template in PHP like in C++

问题

Is is possible to create class template in PHP as in C++? PHP probably does not have a similar language structure (like template key words in C++), but maybe there is some clever trick to achieve similar functionality?

I have a Point class that I would like to convert to a template. In class I use typing arguments, therefore, for each class, I would like to pass to the Point method I have to create a new copy of Point class with appropriate types of arguments.

This is sample form C++:

#include<iostream>

template <typename T>
class Point
{
    public:
    T x, y;

    Point(T argX, T argY)
    {
        x = argX;
        y = argY;
    }
};

int main() {
    Point<int> objA(1, 2);
    std::cout << objA.x << ":" << objA.y << std::endl;

    Point<unsigned> objB(3, 4);
    std::cout << objB.x << ":" << objB.y << std::endl;

    return 0;
}

And the same in PHP, but it not work at all (of course the last but one line returns an error):

class SomeClass
{
    public $value;

    public function __construct($value = 0)
    {
        $this->value = $value;
    }
}

class OtherClass
{
    public $value;

    public function __construct($value = 0)
    {
        $this->value = $value;
    }
}

class Point
{
    public $x;
    public $y;

    public function Point(SomeClass $argX, SomeClass $argY)
    {
        $this->x = $argX;
        $this->y = $argY;
    }
}

$objA = new Point(new SomeClass(1), new SomeClass(2));
echo $objA->x->value . ":" . $objA->y->value . PHP_EOL;

$objB = new Point(new OtherClass(3), new OtherClass(4));
echo $objB->x->value . ":" . $objB->y->value . PHP_EOL;

回答1:

The best you can do is PHP's eval-like features, whereby objects can be instantiated like this:

$className = 'SomeClass';
$obj = new $className;

This, combined with the airy-fairy dynamic typing ought to be enough to allow:

$objA = new Point('SomeClass', 1, 2);
echo $objA->x->value . ":" . $objA->y->value . PHP_EOL;

$objB = new Point('OtherClass', 3, 4);
echo $objB->x->value . ":" . $objB->y->value . PHP_EOL;

The requisite definition may look like this:

class Point
{
    public $x;
    public $y;

    public function __construct($className, $argX, $argY)
    {
        $this->x = new $className($argX);
        $this->y = new $className($argY);
    }
}

I'm not sure I'd promote this sort of code style, though. Your original approach seems clearer and cleaner. You can perform a sanity check inside the Point constructor that both arguments share the same type, if you'd like.

来源：https://stackoverflow.com/questions/21605535/class-template-in-php-like-in-c

标签

php

c++

class-template