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： 

 

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： 

 

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

　　 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： 

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`。

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: 

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
    }
  }
}