Swift - Case 语句和 MetaType 检查？

Question

给定一个字典，我需要检查它的值是字典、数组还是其他。我收到以下错误:

Downcast pattern value of type Dictionary cannot be used

// Type of dictionary to enumerate through
public typealias SourceDictionary = [String: AnyObject]
var dictionary: SourceDictionary


for (key, value) in dictionary {
   switch (value) {
      case value as SourceDictionary :
         print("Dictionary")

      case value as Array :
         print("Array")

      default :
         print("Other")
   }
}

也试过

case let someValue as SourceDictionary

Answer 1

您可以使用 switch 或 if 语句进行检查，只是您的语法不太正确。

切换:

for (key, value) in dictionary {
    switch value {
    case let v as Dictionary<String, AnyObject>:
        println("Dictionary in \(key)")
    default:
        println("other")
    }
}

如果:

for (key, value) in dictionary {
    if let v = value as? Dictionary<String, AnyObject> {
        println("Dictionary in \(key)")
    }
}