Swift相当于为属性设置多个值

Question

我目前正在使用以客观c编写的cocoapod.在示例中,它们显示了类似的内容:

options.allowedSwipeDirections = MDCSwipeDirectionLeft | MDCSwipeDirectionRight;

我甚至不知道调用这些变量是什么,但我已经在Swift中尝试了以下内容:

options.allowedSwipeDirections = MDCSwipeDirection.Left | MDCSwipeDirection.Right

但编译说 No '|' candidates produce the expected contextual result type 'MDCSwipeDirection'

我如何在Swift中执行此操作？

编辑:

看起来这不是OptionSet一些答案中所说的,她是声明:

/*!
 * Contains the directions on which the swipe will be recognized
 * Must be set using a OR operator (like MDCSwipeDirectionUp | MDCSwipeDirectionDown)
 */
@property (nonatomic, assign) MDCSwipeDirection allowedSwipeDirections;

就像这样使用:

_allowedSwipeDirections = MDCSwipeDirectionLeft | MDCSwipeDirectionRight;

Answer 1

MDCSwipeDirection是(不幸的是)在Objective-C中定义为NS_ENUM而不是NS_OPTIONS:

typedef NS_ENUM(NSInteger, MDCSwipeDirection) {
    MDCSwipeDirectionNone = 1,
    MDCSwipeDirectionLeft = 2,
    MDCSwipeDirectionRight = 4,
    MDCSwipeDirectionUp = 8,
    MDCSwipeDirectionDown = 16
};

因此它作为一个简单的导入到Swift enum而不是OptionSetType:

public enum MDCSwipeDirection : Int {

    case None = 1
    case Left = 2
    case Right = 4
    case Up = 8
    case Down = 16
}

因此,你必须与兼顾rawValue的enum <-> Int 转换:

let allowedSwipeDirections =  MDCSwipeDirection(rawValue: MDCSwipeDirection.Left.rawValue | MDCSwipeDirection.Right.rawValue)!

请注意,强制解包不能失败,请参阅例如 如何使用Swift 1.2确定NS_ENUM的未记录值:

... 如果从定义中导入枚举,Swift 1.2现在允许使用任意原始值(基础整数类型)创建枚举变量.NS_ENUM

如果将Objective-C定义更改为

typedef NS_OPTIONS(NSInteger, MDCSwipeDirection) {
    MDCSwipeDirectionNone = 1,
    MDCSwipeDirectionLeft = 2,
    MDCSwipeDirectionRight = 4,
    MDCSwipeDirectionUp = 8,
    MDCSwipeDirectionDown = 16
};

然后导入为

public struct MDCSwipeDirection : OptionSetType {
    public init(rawValue: Int)

    public static var None: MDCSwipeDirection { get }
    public static var Left: MDCSwipeDirection { get }
    public static var Right: MDCSwipeDirection { get }
    public static var Up: MDCSwipeDirection { get }
    public static var Down: MDCSwipeDirection { get }
}

你可以简单地写

let allowedDirections : MDCSwipeDirection = [ .Left, .Right ]