将自定义类型转换为字符串

Question

我有自定义类型：

open class HashTag: Equatable {

    open var text: String
    open var isRemovable: Bool
    open var hasHashSymbol: Bool
    open var configuration: HashtagConfiguration?

    public init(word: String, withHashSymbol: Bool = true, isRemovable: Bool = true) {
        self.text = word
        self.isRemovable = isRemovable
        self.hasHashSymbol = withHashSymbol

        if hasHashSymbol {
            self.text = "#" + text
        }
    }

    public static func == (lhs: HashTag, rhs: HashTag) -> Bool {
        return lhs.text == rhs.text
    }
}

我想把它转成普通的String数组再转回来。例如，对于：

   var tags = [
                HashTag(word: "this"),
                HashTag(word: "is"),
                HashTag(word: "an"),
                HashTag(word: "example")
    ]

我想转移到

var tagsTransferred = ["this","is","an","example"]

然后回传：

var tagsTransferred = ["this","is","an","example"]

到：

   var tags = [
                HashTag(word: "this"),
                HashTag(word: "is"),
                HashTag(word: "an"),
                HashTag(word: "example")
    ]

Answer 1

Array 中的 map 方法用于转换数组的每个元素，即，正是您正在做的事情。

要将[String] 转换为[HashTag]：

let hashTagArray = stringArray.map { HashTag(word: $0) }

将[HashTag] 转换为[String]：

let stringArray = hashTagArray.map { $0.text }

---

此外，如果您希望这样的事情成为可能：

// the string array literal is automatically converted to [HashTag]
let hashTagArray: [HashTag] = ["this", "is", "an", "example"]

你可以这样做：

open class HashTag : Equatable, ExpressibleByStringLiteral {

    ...

    public typealias StringLiteralType = String
    public required convenience init(stringLiteral value: String) {
        self.init(word: value)
    }
}

Answer 2

这两种情况都可以使用compactMap 函数。

1. 从 [HashTag] 到 [String]

   var tags = [
       HashTag(word: "this"), 
       HashTag(word: "is"), 
       HashTag(word: "an"), 
       HashTag(word: "example")
   ]
   
   let arrString = tags.compactMap { (tag) -> String in
       tag.text.removeFirst() // This line just to remove "#"
       return tag.text
   }
   

2. 从 [String] 到 [HashTag]

   var strings = ["this", "is", "an", "example"]
   
   let arrHashtag = strings.compactMap {
       return HashTag(word: $0)
   }