克隆PHP对象并在克隆上设置受保护的属性

Question

I got a logical problem.

I got an object that needs to be cloned.

The object is|has a result of a calculation.

The object has a runtime.

In some cases it is faster to clone the object instead of calculating the result again

(fe same parameter ^= same result) .

But the runtime must not be copied.

The runtime would be the time to determine that i can use the same result (object).

Example:

class Object
{
    protected $runtime;

    public function getRuntime()
    {
        return $this->runtime;
    }

    public function doSome(/*...*/)
    {
        $start = microtime(true);
        // ... the heavy work ...
        // ...
        $this->runtime = microtime(true) - $start;
    }
}

$objects = [];
while (/*...*/) {
    if (count($objects) > 0) {
        $start = microtime(true);
        if (/*check if would get the same result as the previous one*/) {
            $object = clone end($objects);
            // MUST change the runtime here on the clone 
            // but i should not make :runtime public
            $object->runtime = microtime(true) - $start; // :(
            $objects[] = $object;
            continue;
        }
    }
    $object = new Object();
    $object->doSome(/*...*/);
    $objects[] = $object;
}

How could i clone the previous object and set the actual runtime on the clone without making it possible to make the runtime property public?

Answer 1

I would suggest to put this logic in separated method Object::clone() like this:

class Object
{
    protected $runtime;

    public function getRuntime()
    {
        return $this->runtime;
    }

    public function doSome(/*...*/)
    {
        $start = microtime(true);
        // ... the heavy work ...
        // ...
        $this->runtime = microtime(true) - $start;
    }

    public static function clone($clonable, $runtime)
    {
        $clone = clone $clonable;
        $clone->runtime = $runtime; // we can access it since we are in Object scope
        return $clone;
    }
}

$objects = [];
while (/*...*/) {
    if (count($objects) > 0) {
        $start = microtime(true);
        if (/*check if would get the same result as the previous one*/) {
            $object = Object::clone(end($objects), microtime(true) - $start);
            $objects[] = $object;
            continue;
        }
    }
    $object = new Object();
    $object->doSome(/*...*/);
    $objects[] = $object;
}

Another option is just to implement setter method for runtime property

Answer 2

Use the magic method:

Once the cloning is complete, if a __clone() method is defined, then the newly created object's __clone() method will be called, to allow any necessary properties that need to be changed.

http://php.net/manual/en/language.oop5.cloning.php#object.clone

class Object
{
    protected $runtime;

    public function __clone() {
        //set $this->runtime
    }
}