OptionSet and bitwise operator <<

I don't really get OptionSet or bitwise properly. But this is a starting point before starting to google.

OptionSet is a slightly different use case to enum

Imagine you are at a Pizza Hut / Sizzler dessert buffet (if you are a child of the 80s). Otherwise you can imagine you are at a frozen yoghurt place. Much more modern, but no nostalgia there.

You have your soft serve, and you have infinite toppings you can choose from.

This store charges by number of toppings the customer picks, not weight.

So, when you implement it, you could have:

enum Topping {
    case sprinkles
    case honeycomb
    case strawberries
    case cookieDough
    case peanuts
}

Then when comes time to calculate the amount.. you'll need a numberOfToppngs: [Topping?]. Or something like that. Cos the customer may have 0 toppings, or all 5 toppings.

However, if you use an OptionSet, it handles this for you.

I think a better example for OptionSet may be a sushi train. Cos the point of option set is that it could be many things.

10 = you have udon but no sashimi.
11= you have udon AND sashimi

struct SushiOptions: OptionSet {
    static let udon    = SushiOptions(rawValue: 1 << 0)
    static let sashimi  = SushiOptions(rawValue: 1 << 1)
}

I think OptionSet always uses bitwise operations, described here by Apple.

When to use bitwise operators instead of Int? When you care about speed, e.g. when you are working with video or audio, speed matters.