Bitmask.m

typedef NS_OPTIONS(NSUInteger, LSRBorderSide) {
    LSRBorderSideNone   = 1 << 0,
    LSRBorderSideLeft   = 1 << 1,
    LSRBorderSideRight  = 1 << 2,
    LSRBorderSideBottom = 1 << 3,
    LSRBorderSideTop    = 1 << 4
};

Bitmask.swift

//Nasty implementation of NS_Option for Swift.
struct Border : RawOptionSetType, BooleanType {
    
    //Detailed protocol implementation of RawOptionSetType which is a collection of protocols listed here -> _RawOptionSetType, BitwiseOperationsType, NilLiteralConvertible
    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: Border { return self(0) }
    static func fromMask(raw: UInt) -> Border { return self(raw) }
    var rawValue: UInt { return self.value }
    
    //Implementation of BooleanType protocol
    var boolValue:Bool { get { return self.value != 0 }}
    
    static var None: Border { return self(0) }
    static var Left: Border { return Border(1 << 0) }
    static var Right: Border { return Border(1 << 1) }
    static var Bottom: Border { return Border(1 << 2) }
    static var Top: Border { return Border(1 << 3) }
}