Swift 元组作为字典值

Question

我有以下 class，它使用下标作为其本质上对 Swift 字典的包装。

class STCTruthDict: NSObject, SequenceType {

  typealias IpRelationshipTuple = (String, String?)

  private var truthDict: [String : IpRelationshipTuple] = [ : ]

  subscript(key: String) -> IpRelationshipTuple? {
    get {
        return self.truthDict[key]
    }
    set {
        truthDict[key] = newValue
    }
  }

  // MARK: - Initializers

  override init() {
      super.init()
  }

func generate() -> DictionaryGenerator <String, IpRelationshipTuple> {
    return self.truthDict.generate()
}

}

我正在尝试通过以下代码使用此 class 及其来自另一个 class 的下标：

private var truthDict: STCTruthDict?
.....
.....
.....

 // Get ip and userId
 let ipToBeAdded = responseData["ip"] as! String
 let userIdForIP = responseData["user_id"] as! String
 // update truth table
 let relationshipTuple = (ipToBeAdded, nil) as STCTruthDict.IpRelationshipTuple?
 self.truthDict[userIdForIP] = relationshipTuple

但我收到一条错误消息：

“Cannot assign to immutable value of type ‘IpRelationshipTuple?’ “

谁能告诉我我做错了什么？

这是游乐场快照：

Answer 1

因为您的 truthDict 被定义为可选的，您需要将其解包。我没有得到与你相同的错误，但你应该尝试 truthDict!["you"] 或从定义中完全删除可选。

var truthDict = STCTruthDict()

或

truthDict!["you"] = relationshipTuple
//       ^

Swift 元组作为字典值

Swift tuple as dictionary value

ios

swift

xcode6