Updated September 30 for Swift 1.1b3 compatibility.

Swift has an great enumeration type built in, so it isn’t surprising that NS_ENUM-style enumerations are automatically bridged from Objective-C and similar ones are easy to create by hand. NS_OPTIONS-style bitmasks, on the other hand, are a little harder to create for yourself. I looked through the bitmask options that Swift imports from Objective-C (UIViewAutoresizing, for example), and found that options are declared as a struct that conforms to protocol RawOptionSetType, which in turn conforms to _RawOptionSetType, Equatable, RawRepresentable, BitwiseOperationsType, and NilLiteralConvertible.

It’s a bit of a mess to write out, with a lot of repetition, so I’ve created a generator for NS_OPTIONS bitmasks in Swift. Just enter the name of your options type and the list of options, then copy the customized code!

Note: As of beta 6, RawOptionSetType no longer implements BooleanType by default, so standard bitmask checks (if opt & .Option {...) only work if you add BooleanType protocol conformance manually.

struct MyOptions : RawOptionSetType {
    typealias RawValue = UInt
    private var value: UInt = 0
    init(_ value: UInt) { self.value = value }
    init(rawValue value: UInt) { self.value = value }
    init(nilLiteral: ()) { self.value = 0 }
    static var allZeros: MyOptions { return self(0) }
    static func fromMask(raw: UInt) -> MyOptions { return self(raw) }
    var rawValue: UInt { return self.value }
    
    static var None: MyOptions { return self(0) }
    static var Option: MyOptions { return self(1 << 0) }
}

Please let me know if you find this useful!