Weekly Swift articles, podcasts and tips by John Sundell.

Defining custom option sets

Published on 12 Jan 2018

The awesome thing about option sets in Swift is that they can automatically either be passed as a single member or as a set. Even cooler is that you can easily define your own option sets as well, perfect for options and other non-exclusive values.

// Option sets are awesome, because you can easily pass them
// both using dot syntax and array literal syntax, like when
// using the UIView animation API:
UIView.animate(withDuration: 0.3,
               delay: 0,
               options: .allowUserInteraction,
               animations: animations)

UIView.animate(withDuration: 0.3,
               delay: 0,
               options: [.allowUserInteraction, .layoutSubviews],
               animations: animations)

// The cool thing is that you can easily define your own option
// sets as well, by defining a struct that has an Int rawValue,
// that will be used as a bit mask.
extension Cache {
    struct Options: OptionSet {
        static let saveToDisk = Options(rawValue: 1)
        static let clearOnMemoryWarning = Options(rawValue: 1 << 1)
        static let clearDaily = Options(rawValue: 1 << 2)

        let rawValue: Int
    }
}

// We can now use Cache.Options just like UIViewAnimationOptions:
Cache(options: .saveToDisk)
Cache(options: [.saveToDisk, .clearDaily])