再帰的なEnumを、structに変換する

Recursive_enum_struct_translation.swift

indirect enum TreeEnum{
    case leaf(id:String, body:String)
    case multiPart(id:String, body:[TreeEnum])
    case message(id:String, body:TreeEnum)
}

struct Root{
    let id:String
    let body:String?
    
    let parts:[Root]?
}

//struct Part<T>{//TはRootかPart
//    let parentPart:T
//    let parts:[Part]?
//
//    let id:String
//    let body:String?
//}

//: Compose Enums
let leaf1 = TreeEnum.leaf(id: "leaf1", body: "body1")
let leaf2 = TreeEnum.leaf(id: "leaf2", body: "body2")
let leaf3 = TreeEnum.leaf(id: "leaf3", body: "body3")
let leaf4 = TreeEnum.leaf(id: "leaf4", body: "body4")
let node = TreeEnum.multiPart(id: "node", body: [leaf2,leaf3,leaf4])

let root = TreeEnum.multiPart(id: "root", body: [leaf1, node])

//: Translate enum to structs
func translate(treeEnum:TreeEnum)->Root{
    switch treeEnum {
    case let .leaf(id,body):
        return Root(id: id, body: body, parts: nil)
        
    case let .multiPart(id, enumArray):
        return Root(id: id,
                    body: nil,
                    parts: enumArray.map{translate(treeEnum: $0)})
        
    case let .message(id,treeEnum):
        return Root(id:id,
                    body:nil,
                    parts: [translate(treeEnum:treeEnum)])
    }
}


let translatedRoot = translate(treeEnum: root)


//: do some job with translated struct
extension Root{
    var description:String{
        
        var string = ""
        
        //まず自分自身の情報を追加
        string.append("id: " + self.id + ", body: " + (self.body ?? "parts") + "\n")
        
        //partsが存在すれば、partsの情報を追加
        if let parts = self.parts{
            
            let partsString = parts.reduce(""){(result ,part) in
                result + part.description
            }
            
            string.append(partsString)
        }
    
        return string
    }
}

print(translatedRoot.description)

RecursiveEnum.md

再帰的なEnumに関係する情報

inamiy

• Algebraic Data Type in Swift // Speaker Deck
• Result V.S. Result<T, E> // Speaker Deck
• Swift 2 Error Handling vs Result<T, E> // Speaker Deck