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20.Swift位移枚举
typedef NS_OPTIONS(NSUInteger, UIRectCorner) {
UIRectCornerTopLeft = 1 << 0,
UIRectCornerTopRight = 1 << 1,
UIRectCornerBottomLeft = 1 << 2,
UIRectCornerBottomRight = 1 << 3,
UIRectCornerAllCorners = ~0UL
};
[view addRoundedCorners:(UIRectCornerTopLeft | UIRectCornerTopRight) withRadii:CGSizeMake(12.f, 12.f)];
public struct UIRectCorner : OptionSet {
public init(rawValue: UInt)
public static var topLeft: UIRectCorner { get }
public static var topRight: UIRectCorner { get }
public static var bottomLeft: UIRectCorner { get }
public static var bottomRight: UIRectCorner { get }
public static var allCorners: UIRectCorner { get }
}
$0.addRoundedCorners([.topLeft, .topRight], withRadii: CGSize(width: 15, height: 15))
发现在Swift中它并不是枚举，而是装换为了
结构体，使用的API出则是转换为了对应元素类型的数组。 我们需要自定义位移枚举的时候可以参考系统的这种实现方式。如：
struct Sports: OptionSet {
let rawValue: Int
static let running = Sports(rawValue: 1)
static let cycling = Sports(rawValue: 2)
static let swimming = Sports(rawValue: 4)
static let fencing = Sports(rawValue: 8)
static let shooting = Sports(rawValue: 32)
static let horseJumping = Sports(rawValue: 512)
}
当然部分API并没有经过上面的这种转化，如： 下面就是我在异步处理图片的时候遇到的一个场景
let bitmapInfo: CGBitmapInfo = CGBitmapInfo(rawValue: hasAlpha ? CGImageAlphaInfo.premultipliedFirst.rawValue : CGImageAlphaInfo.noneSkipFirst.rawValue).union(.byteOrder32Little)
正如注释中所说：
A new option set made up of the elements contained in this set, in other, or in both.