Swift位移枚举 - Lab.Lawliet

300 字

2 分钟

Swift位移枚举

2021-03-29

2026-10-12

Swift

无标签

一：以系统中的一个位移枚举为例#

a. OC版本#

1
typedef NS_OPTIONS(NSUInteger, UIRectCorner) {
2
    UIRectCornerTopLeft     = 1 << 0,
3
    UIRectCornerTopRight    = 1 << 1,
4
    UIRectCornerBottomLeft  = 1 << 2,
5
    UIRectCornerBottomRight = 1 << 3,
6
    UIRectCornerAllCorners  = ~0UL
7
};

1
[view addRoundedCorners:(UIRectCornerTopLeft | UIRectCornerTopRight) withRadii:CGSizeMake(12.f, 12.f)];

b.Swift版本#

1
public struct UIRectCorner : OptionSet {
2
    public init(rawValue: UInt)
3

4
    public static var topLeft: UIRectCorner { get }
5

6
    public static var topRight: UIRectCorner { get }
7

8
    public static var bottomLeft: UIRectCorner { get }
9

10
    public static var bottomRight: UIRectCorner { get }
11

12
    public static var allCorners: UIRectCorner { get }
13
}

1
$0.addRoundedCorners([.topLeft, .topRight], withRadii: CGSize(width: 15, height: 15))

c.分析#

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：

1
struct Sports: OptionSet {
2
    let rawValue: Int
3

4
    static let running = Sports(rawValue: 1)
5
    static let cycling = Sports(rawValue: 2)
6
    static let swimming = Sports(rawValue: 4)
7
    static let fencing = Sports(rawValue: 8)
8
    static let shooting = Sports(rawValue: 32)
9
    static let horseJumping = Sports(rawValue: 512)
10
}

二：Swift#

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

1
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.

iOS应用签名原理

知识点梳理：算法数据结构