类型 'NSObject?' 没有下标成员

Question

我已经搜索过了，真的，在这里问问题是我最后的选择......老实说，但是自从 "I had to ask" 以来，请随意对我投反对票。 .! 现在进入正题...

我有一个有两个级别的字典 "dict > keys"，就是这样！但无论出于何种原因，我似乎无法获得 "three" 值。我哪里错了？

print(mainDict)

/*
 ["keys": {
     one = "one...";
     two = 2;
     three = "three"; // need this one!
 }]
*/

let sub = mainDict["keys"]
print(sub as Any)

/*
 Optional({
     one = "one...";
     two = 2;
     three = "three";
 })
*/

太棒了！到目前为止一切顺利...但是：

let keyThree = mainDict["three"]
print(keyThree as Any)
// nil

let keyThree = sub["three"]
// Type 'NSObject?' has no subscript members

什么？ ...尝试过：

Why do I have "type 'NSObject' has no subscript members" error?
[NSObject : AnyObject]?' does not have a member named 'subscript' in Xcode 6 Beta 6

Answer 1

函数签名中mainDict的声明必须是[String :[String:Any]]。或者您可以将其声明为 [String:Any] 然后，您需要将 sub 转换为 [String:Any]

所以函数应该是

func makeItPossible(mainDict : [String:Any]){
   if let sub= mainDict["keys"] as [String:Any], let keyThree = sub["three"]{
        print(keyThree)
}

更新为使用条件绑定。

类型 'NSObject?' 没有下标成员

Type 'NSObject?' has no subscript members

macos

xcode

swift

swift3

macos-sierra