How to migrate a java command pattern using runnable to PHP 7.4?

Question

For studying purpose, I am trying to migrate this Java Command Pattern example to PHP:

https://codereview.stackexchange.com/questions/52110/command-pattern-implementation

As @simon commented, using method reference operator, would modernize quite a bit the code:

class MyCommand implements Order {
    private final Runnable action;

    public MyCommand(Runnable action) {
         this.action = action;
    }

    @Override
    public void execute() {
         action.run();
    }
}

And then you could create commands like this:

MyCommand bsc = new MyCommand(stock::buy);
MyCommand ssc = new MyCommand(stock::sell);

My current PHP implementation is here: https://3v4l.org/iIHn9

So what is the best approach to implement the MyCommand Class in PHP?

Answer 1

As Evgeniy already mentioned you can use call_user_func().

Since there is many ways how to solve this I've added my solutions to your question. You can also make an object callable by adding the __invoke method inside a class. It's also possible to return a callable function. I've added in total 3 examples for it.

This is my version of your MyCommand class in java which is used for all 3 examples.

class MyCommand implements Order
{
    private $action;

    public function __construct(callable $action)
    {
        $this->action = $action;
    }

    public function execute()
    {
        // Option 1) use call_user_function
        call_user_func($this->action);

        // Option 2) define it as a variable and call it by adding `()`
        //$action = $this->action;
        //$action();
    }
}

Example 1) A callable function (https://3v4l.org/FVTEK)

class Stock
{
    public function buy(): callable
    {
        return function () {
            echo "You want to buy stocks via callable function" . PHP_EOL;
        };
    }

    public function sell(): callable
    {
        return function () {
            echo "You want to sell stocks via callable function" . PHP_EOL;
        };
    }
}

$stock = new Stock();
$bsc = new MyCommand($stock->buy());
$ssc = new MyCommand($stock->sell());

$bsc->execute();
$ssc->execute();

Example 2) A callable class (https://3v4l.org/BrKjv)

class StockBuy
{
    public function __invoke()
    {
        echo "You want to buy stocks via __invoke()" . PHP_EOL;
    }
}

class StockSell
{
    public function __invoke()
    {
        echo "You want to sell stocks __invoke()" . PHP_EOL;
    }
}

$bsc = new MyCommand(new StockBuy());
$ssc = new MyCommand(new StockSell());

$bsc->execute();
$ssc->execute();

Example 3) Static member functions which return callable. Just an example to be more close to java (https://3v4l.org/PKk4B)

class Stock
{
    static public function buy(): callable
    {
        return function () {
            echo "You want to buy stocks via callable function" . PHP_EOL;
        };

        // or as callable object
        // return new StockBuy();
    }

    static public function sell(): callable
    {
        return function () {
            echo "You want to sell stocks via callable function" . PHP_EOL;
        };

        // or as callable object
        // return new StockSell();
    }
}

$bsc = new MyCommand(Stock::buy());
$ssc = new MyCommand(Stock::sell());
$bsc->execute();
$ssc->execute();

Please let me know if you have any further questions.