Raw value for enum case must be a literal

Question

I have this enum:

enum GestureDirection:UInt {
    case Up =       1 << 0
    case Down =     1 << 1
    case Left =     1 << 2
    case Right          


        

Answer 1

For attributes which are not mutually exclusive I would also recommend to use a struct based on RawOptionSetType as @Vincent suggested. One advantage is that you get all bit operations for free.

Here is a full working example:

struct GestureDirection : RawOptionSetType {
    let rawValue : UInt8
    init(rawValue: UInt8) {
        self.rawValue = rawValue
    }

    init(nilLiteral: ()) {
        self.rawValue = 0
    }
    static var allZeros: GestureDirection { return self(rawValue: 0) }

    static var Top:   GestureDirection { return self(rawValue: 1 << 0) }
    static var Down:  GestureDirection { return self(rawValue: 1 << 1) }
    static var Left:  GestureDirection { return self(rawValue: 1 << 2) }
    static var Right: GestureDirection { return self(rawValue: 1 << 3) }
}

Usage:

// Initialize:
var direction : GestureDirection = .Top | .Right

// Test:
if (direction & .Top) != nil {
   // ...
}

// Add an option:
direction |= .Left

// Remove an option:
direction &= ~(.Right)

---

Update for Swift 2: As of Swift 2, this can be simpler done with the new OptionSetType protocol, which offers a set-like interface (see also the recently added answers to How to create NS_OPTIONS-style bitmask enumerations in Swift?).

We just have to define the underlying storage type and the pre-defined values:

struct GestureDirection : OptionSetType {
    let rawValue : UInt8

    static let Top   = GestureDirection(rawValue: 1 << 0)
    static let Down  = GestureDirection(rawValue: 1 << 1)
    static let Left  = GestureDirection(rawValue: 1 << 2)
    static let Right = GestureDirection(rawValue: 1 << 3)
}

Usage:

// Initialize:
var direction : GestureDirection = [ .Top, .Right ]

// Test:
if direction.contains(.Top) {
    // ...
}

// Add an option:
direction.insert(.Left)

// Remove an option:
direction.remove(.Right)