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Discussion on: My opinion on the PHP 8.1 Enum RFC

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nicolus profile image
Nicolas Bailly • • Edited

Yeah I agree with you. I had not read the whole RFC, just the first few points and thought it was great (kinda like class constants on steroids). After reading your post I went back to the RFC and read the whole thing... And either this tries to cover some very limited use cases, or I don't understand the point of Enums.

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rvxlab profile image
RVxLab •

Enums are particularly useful when you need to enforce a subset of items that are valid.

Let’s say you have a button that can have 4 different colours. You could make those colours an enum. Or it can have 1 of 3 sizes, that could be an enum.

Or as in the RFC, a suit can be an enum.

Now you can also solve this by just using a string, but what do you do when someone puts in an invalid value? You’d need to check for that. If you use an enum that check already happens during typechecking.

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nicolus profile image
Nicolas Bailly • • Edited

Yes I think get that part, that's what I called 'class constants on steroids'. What I would do in PHP 7 is something like :

class Card
{
    const DIAMONDS = 'diamonds';
    const HEARTS   = 'hearts';
    const SPADES   = 'spades';
    const CLUBS    = 'clubs';

    const SUITS = [
        self::DIAMONDS,
        self::HEARTS,
        self::SPADES,
        self::CLUBS,
    ];


    public function __construct($suit)
    {
        if (!in_array($suit, self::SUITS)) {
            throw new InvalidArgumentException('invalid suit');
        }
    }
}

//works
$card = new Card(Card::SPADES);

//works :
$card = new Card('spades');

//throws an exception :
$card = new Card('hammers');
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With Enums it becomes a lot easier as you said.

But I don't need to put methods on my enums for that ! If I want a method that returns the shape or color of a suit I'll just create a Suit interface with a abstracts shape() and color() method and implement that method in a Spade class.
In the RFC they have an example where the color method uses a match statement to return the color and always return 'rectangle' as a shape. To me this kind of defeats the purpose of OOP.