Raw value是 一种 特殊的Associated Values ,使用起来简单,适用于通常的enum场景。一个enum只能有一个Raw value类型,每个case的 rawValue都有 default 值,不必写代码动态指定。对于Int和String类型的rawValue,可以不把每个case都指定默认值,系统可以进行推算。从case值里面取rawValue也十分简单,不必再放入switch case ...
Enum associated valuesQuestion 1/6: Which of these create enums with an associated value?Hint: Click to show.Option 1:enum Building { case skyscraper(floors: Int) }Option 2:enum role { case administrator }Choose Option 1 Choose Option 2 ...
How to save enum with associated value in UserDefaults For demonstration, we create a Role enum to keep a user's role. enum Role { case guest case member(String?)} If we save this enum to UserDefaults, you will get a runtime exception. UserDefaults.standard.set( Role.guest, forKey: ...
enumCompassPoint:String{caseNorth,South,East,West} 上面例子中,CompassPoint.South拥有隐式初值South,依次类推。 使用枚举成员的rawValue属性可以访问该枚举成员的原始值: letearthsOrder=Planet.Earth.rawValue// earthsOrder 值为 3letsunsetDirection=CompassPoint.West.rawValue// sunsetDirection 值为 "West" 使...
如果想要以底层 C 二进制编码形式呈现某物或某事,使得更具可读性,可以看一下 BSD kqeue library 中的 VNode Flags 标志位的编码方式,如此便可以使你的 Delete 或 Write 用例声明一目了然,稍后一旦需要,只需将 raw value 传入 C 函数中即可。 enum VNodeFlags: UInt32 { case delete = 0x00000001 case wri...
关联值(Associated Value)关联值是将额外信息附加到enum case中的一种极好的方式。打个比方,你正在开发一款交易引擎,可能存在买和卖两种不同的交易类型。除此之外每手交易还要制定明确的股票名称和交易数量:简单例程(Simple Example)enum Trade { case Buy case Sell } func trade(tradeType: Trade, stock: String...
枚举(enum) -- 掌握基本概念和语法所谓枚举-- 是一种取值范围固定在某个指定集当中的数据类型。 定义的语法: public enum枚举类型名{值选项1,值选项2,...,值选项n; } 注意点: 1、这里的值选项是标识符,不是字符串; 2、这里的值选项是有顺序的; 3、值选项不能重复。使用的语法:枚举类型 变量 =枚举...
enumPizza{ casesmall(inches:Int) } 在这里,我们为关联值提供了名称inches。 当读取指定的关联值而不是 casesmall(Int) 实例:命名关联值 enumPizza{ // named associated value casesmall(inches:Int) casemedium(inches:Int) caselarge(inches:Int)
Swift Enum cases are only equatable if all associated values are. More specifically, the error reads as follows: Binary operator ‘==’ cannot be applied to two ‘AppNotification’ operands To resolve this, we make the UserInfo struct conform to Equatable and explicitly declare the enum’s Equa...
enum ColorSpace { case rgba(red: UInt8, green: UInt8, blue: UInt8, alpha: Float) case cmyk(cyan: Float, magenta: Float, yellow: Float, black: Float) } Not too daunting, but there are a few things to take note of. First, there is no raw value type after the enumeration as we...