/php-ad-hoc-polymorphism-polyfill

Polyfill of missing in PHP ad-hoc polymorphism

Primary LanguagePHP

Why?

PHP don't knows what is Ad hoc polymorphism. When Java and other higher level languages knows about it:

class Overload
{
  void demo (int a)
  {
   System.out.println ("a: " + a);
  }
  void demo (int a, int b)
  {
   System.out.println ("a and b: " + a + "," + b);
  }
  double demo(double a) {
   System.out.println("double a: " + a);
   return a*a;
  }
}

So here we are trying to provide somekind of polyfill in PHP.

Show me the code

Assume you have class which can do something with Iterators:

interface IteratorCaller
{
  public function callMe(Iterator $i);
}

And you want to process different iterators differently. In ad-hoc polymorphism world you can just define different callMe methods with concrete Iterator signatures. In PHP world you can't do this. One possible way is to go by the "instanceof" way, which would be probably a code smell.

So it's time to try Polycall:

use Garex\Adhoc2p\Polycall;

class IteratorCallerImpl implements IteratorCaller
{

  public function callMe(Iterator $i)
  {
    $_p = (new Polycall($this))
      ->on(ArrayIterator::class)->to('callMe0')
      ->on(DirectoryIterator::class)->to('callMe1')
    ;
    return $_p->go(func_get_args());
  }

  public function callMe0(ArrayIterator $i)
  {
    return 'ArrayIterator';
  }

  public function callMe1(DirectoryIterator $i)
  {
    return 'DirectoryIterator';
  }
}

What about optimizations?

One time init

  public function callMe(Iterator $i)
  {
      static $_p = null;
      if (!is_null($_p)) {
          return $_p->go(func_get_args());
      }
      
      $_p = (new Polycall($this))
          ->on(ArrayIterator::class)->to('callMe0')
          ->on(ArrayIterator::class)->to('callMe1')
      ;
      return $_p->go(func_get_args());
  }

Guess overloaded methods names

  public function callMe(Iterator $i)
  {
    $_p = (new Polycall\AutoTo($this, __METHOD__))
      ->on(ArrayIterator::class)
      ->on(DirectoryIterator::class)
    ;
    return $_p->go(func_get_args());
  }

Guess overloaded methods names

  public function callMe(Iterator $i)
  {
    $_p = (new Polycall\AutoTo($this, __METHOD__))
      ->on(ArrayIterator::class)
      ->on(DirectoryIterator::class)
    ;
    return $_p->go(func_get_args());
  }

Preconfigure polycall object in callable

  use Polycall\Inside;
  
  public function callMe(Iterator $i)
  {
    return $this->polycallGo(func_get_args(), $method = __METHOD__, function() use ($method) {
      return (new Polycall\AutoTo($this, $method))
        ->on(ArrayIterator::class)
        ->on(DirectoryIterator::class)
      ;
    });
  }