对于Swift的Enum,文档上没有说的

今天无意发现一个东西， 但是在文档上看了很多遍都没找到， 但是亲测是可行的， 那到底是什么呢？

以前我们定义枚举 会这样： 

 

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enum Hello {     case Item( String,  Int)     case Healthy( Float,  Float) }

 文档上也是这么写的，但是在开发中，例如： 

 

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enum FeastTransform {                             //(let cityID: Int?, let catoryID: Int?, let typeID: Int? , let sort: String?, let number: String?, let time: String, let cdbID: Int, let placeTypeID: Int, let banner: Int, let nextCursor: String, count:Int)         case ThemesOfPublicT(Int, Int, Int, String, String, String, Int, Int, Int, String, Int)                   case ThemesOfPublic(String, Int?, ID , Count, List?)         case Theme(ID)         case ThemesOfMaster(ID, ID)         case ThemesOfParticipator(ID, ID)         case ThemesOfMyself(String?, ID, Count)         case ThemesOfMasterBookable(ID)         case ThemesUpdate(ID, String, String, String, String,             String, DictArray, DictArray)        }

 为了可读性，我们顶多做到就是用

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typealias ID = String  typealias Name = String  typealias URL = String  typealias Count = Int  typealias Price = String  typealias KeyWorkds = String  typealias List = Array<String>

 但是上面的可读性还是 so ugly!

但是今天无意发现这么个东西，😄。真的不要谢我，真心是无意的。原来枚举可以这么玩： 

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enum Hello {       case Item(name: String, age: Int)       case Healthy(height: Float, weight: Float)   }

 给他的参数命名， 玩过Haskell的伙伴应该说句  nice！这个真心nice，可读性立马 提升到一个水平， 都不用这个 `typealias KeyWorkds = String`。

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extension Hello {     func para() -> Dictionary<String, Any> {         switch self {         case .Item(let name , let age):             return ["name": name, "age": age]                       case .Healthy(let height, let weight):             return ["height": height, "weight":weight]         }     }       }   let a = Hello.Healthy(height: 12, weight: 13) a.para()

 有兴趣的伙伴们也可以试试哇.

 

 使用Where语句: 

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extension Media {   var publishedAfter1930: Bool {     switch self {     case let .Book(_, _, year) where year > 1930: return true     case let .Movie(_, _, year) where year > 1930: return true     case .WebSite: return true // same as "case .WebSite(_)" but we ignore the associated tuple value     default: return false     }   } }