Swift 4.1 - 无法将[Character]类型的值转换为[String]

Question

我的代码之前支持Swift 3.3，现在我使用Xcode 9.3将其升级到Swift 4.1。它在尝试构建项目时向我显示以下错误。

以下是JSON解析的代码

    // MARK: Store JSON initializer

      convenience init?(withJSON json: JSON) {
        //json mapping 
        //This is of type [Character] after mapping
        let services = json["services"].arrayValue.flatMap({ $0 }).flatMap({ $0.1.stringValue }) //Convert response to 1D array and convert it to array if String

    }

这是我尝试调用

的init方法

//Custom init method

  init(id: Int, storeNumber: String, title: String, location: Location, type: String, zip: String, parent: Int, city: String, services: [String], state: String, storePhone: [String], pharmacyPhone: [String], pharmacyFax: [String], workingHours: WorkingHoursString) {

    //field with error
    //here self.services is of type [String]
    self.services = services
  }

我正在使用 pod＆＃39; SwiftyJSON＆＃39;，＆＃39; 3.1.4＆＃39; 用于Json解析。

  

错误 - 无法转换类型＆＃39; [字符]＆＃39;的值预期的论点   键入＆＃39; [String]＆＃39;

/* JSON for services is as given

    "services":[
     [
     "Fresh Food"
     ]
    ]

*/
    print("Services are \(services)")
    Services are ["F", "r", "e", "s", "h", " ", "F", "o", "o", "d"]

解决这个问题的最简单的解决办法是什么？

Answer 1

在以下代码中可以观察到相同的行为：

let services: [[String: Any]?] = [
    ["service1": "service1-name"],
    ["service2": "service2-name"]
]

let result = services
    .flatMap({ $0 })
    .flatMap({ $0.1 as! String })
print(result)

我认为这是由Swift 4中String和Dictionary的多项更改引起的（例如，String成为Collection个字符。在上面的代码中，第一个flatMap将字典合并（展平）为一个字典，第二个flatMap将每个值作为String并将它们展平为2D Collection Character。

我想你想要这样的东西：

let result = services
    .compactMap { $0 } // remove nil dictionaries
    .flatMap { // take all dictionary values as strings and flatten them to an array
       $0.values.map { $0.stringValue }
    }
print(result)

此行给出一个字符串数组，预期结果

let services = json["services"]
    .arrayValue
    .flatMap { $0.arrayValue }
    .map { $0.stringValue }