为什么我要强制转换 String？对于 Any，Xcode 会发出警告，但对于 AnyObject 则不会？

Question

此代码给出警告 "Expression implicitly coerced from 'String?' to Any."

let email : String?;
let password : String?;
let dict = ["email": email, "password": password] as [String: Any];

但是这段代码没有。

let email : String?;
let password : String?;
let dict = ["email": email, "password": password] as [String: AnyObject];

为什么？我怎样才能让 Any 不会因为 AnyObject?

等选项的警告而打扰我

编辑：

这段代码也没有给出警告：

let email : String;
let password : String;
let dict = ["email": email, "password": password] as [String: Any];

但在这种情况下，我需要能够合并对象和可选性。似乎仅当变量类型都是对象和可选时才会出现警告。

Answer 1

根据 Swift Language Guide，当您将可选类型转换为 Any 时，您应该会收到警告（请参阅页面底部的注释）。您可以通过将可选值转换为 Any 来消除警告，如下所示。

let email : String?;
let password : String?;
let dict = ["email": email as Any, "password": password as Any] as [String: Any];

Why if I typecast String? to Any, Xcode gives off warning, but not with AnyObject?