對於Swift的Enum,文檔上沒有說的

今天無心發現一個東西， 可是在文檔上看了不少遍都沒找到， 可是親測是可行的， 那究竟是什麼呢？

之前咱們定義枚舉 會這樣： 

 

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

 文檔上也是這麼寫的，可是在開發中，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)
 
    }

 爲了可讀性，咱們頂多作到就是用

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

 可是上面的可讀性仍是 so ugly!

可是今天無心發現這麼個東西，😄。真的不要謝我，真心是無心的。原來枚舉能夠這麼玩： 

enum Hello {

    case Item(name: String, age: Int)

    case Healthy(height: Float, weight: Float)

}

 給他的參數命名， 玩過Haskell的夥伴應該說句  nice！這個真心nice，可讀性立馬 提高到一個水平， 都不用這個 `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()

 有興趣的夥伴們也能夠試試哇.

 

 使用Where語句: 

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
    }
  }
}