在Swift中声明并使用位域枚举 [英] Declaring and using a bit field enum in Swift

问题描述

如果声明这样的枚举可以正常工作，但是共同尝试使用OR 2值无法编译： p>

 枚举MyEnum：Int 
 {
 case One = 0x01 
 case Two = 0x02 
案例四= 0x04 
案例八= 0x08 
} 
 
 //按照预期的方式工作
 let m1：MyEnum = .One 
 
 //编译器错误：无法找到接受提供的参数的'|'的重载
 let combined：MyEnum = MyEnum.One | MyEnum.Four 
  

我看了一下Swift如何导入基础枚举类型，它通过定义一个 struct 符合 RawOptionSet 协议：

  struct NSCalendarUnit：RawOptionSet {
 init（_ value：UInt）
 var value：UInt 
 static var CalendarUnitEra：NSCalendarUnit {get} 
 static var CalendarUnitYear ：NSCalendarUnit {get} 
 // ... 
} 
  

RawOptionSet 协议是：

 协议RawOptionSet：LogicValue，Equable {
类func fromMask（raw：Self.RawType） - >自我
} 
  

然而，这个协议没有文档，我不能如何实现它自己。此外，还不清楚这是否是Swift官方实施位字段的方法，或者这只是Objective-C桥如何代表它们。

解决方案

您可以构建符合 RawOptionSet 协议的 struct ，您将可以使用它像内置的枚举类型，但与位掩码功能一样。这里的答案显示如何：
Swift NS_OPTIONS风格的位掩码枚举。

How should bit fields be declared and used in Swift?

Declaring an enum like this does work, but trying to OR 2 values together fails to compile:

enum MyEnum: Int
{
    case One =      0x01
    case Two =      0x02
    case Four =     0x04
    case Eight =    0x08
}

// This works as expected
let m1: MyEnum = .One

// Compiler error: "Could not find an overload for '|' that accepts the supplied arguments"
let combined: MyEnum = MyEnum.One | MyEnum.Four

I looked at how Swift imports Foundation enum types, and it does so by defining a struct that conforms to the RawOptionSet protocol:

struct NSCalendarUnit : RawOptionSet {
    init(_ value: UInt)
    var value: UInt
    static var CalendarUnitEra: NSCalendarUnit { get }
    static var CalendarUnitYear: NSCalendarUnit { get }
    // ...
}

And the RawOptionSet protocol is:

protocol RawOptionSet : LogicValue, Equatable {
    class func fromMask(raw: Self.RawType) -> Self
}

However, there is no documentation on this protocol and I can't figure out how to implement it myself. Moreover, it's not clear if this is the official Swift way of implementing bit fields or if this is only how the Objective-C bridge represents them.

解决方案

You can build a struct that conforms to the RawOptionSet protocol, and you'll be able to use it like the built-in enum type but with bitmask functionality as well. The answer here shows how: Swift NS_OPTIONS-style bitmask enumerations.

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