Generic types

Generic types allow us to reuse the same code for different types. The implementation of generic types is usually based on a template. For a given type or class, we generate a T template, which can be used safely further.

Generic types do not exist in PHP. In 2016 this RFC was created, but at this moment it is not known if and when it will be implemented.

Munus uses docblock from PHPStan or Psalm. We can use this tools to analyse our code for type safe. In the following example, we will declare a template type T for Value class, and use it in get method as return param:

/**
 * @template T
 */
class Value
{
    /** @var T */
    private $value;
    
    /**
     * @param T $value
     */
    public function __construct($value) {
        $this->value = $value;
    }

    /**
     * @return T
     */
    public function get()
    {
        return $this->value;
    }
}

Now Value is our generic wrapper for any kind of type. For example we can create Value of int, string or even DateTime type.

$int = new Value(42);
$int->get(); // static analysis tool will now that get returns int

$string = new Value('munus');
$string->get(); // static analysis tool will now that get returns string

$date = new Value(new \DateTime());
$date->get(); // static analysis tool will now that get returns DateTime

Each Value in Munus is generic.