快速案例声明和MetaType检查？

Question

给定一个字典，我需要检查该值是否是Dictionary、Array或其他。我得到以下错误：

无法使用“类型字典”的向下转换模式值

// 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语句检查，您的语法只是不太正确。

开关：

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)")
    }
}