是否有一种方法可以在swift中打印变量的运行时类型?例如:
var now = NSDate()
var soon = now.dateByAddingTimeInterval(5.0)
println("\(now.dynamicType)")
// Prints "(Metatype)"
println("\(now.dynamicType.description()")
// Prints "__NSDate" since objective-c Class objects have a "description" selector
println("\(soon.dynamicType.description()")
// Compile-time error since ImplicitlyUnwrappedOptional<NSDate> has no "description" method
在上面的例子中，我正在寻找一种方法来显示变量“soon”的类型是ImplicitlyUnwrappedOptional<NSDate>，或至少NSDate!
当前回答
斯威夫特3.0
let string = "Hello"
let stringArray = ["one", "two"]
let dictionary = ["key": 2]
print(type(of: string)) // "String"
// Get type name as a string
String(describing: type(of: string)) // "String"
String(describing: type(of: stringArray)) // "Array<String>"
String(describing: type(of: dictionary)) // "Dictionary<String, Int>"
// Get full type as a string
String(reflecting: type(of: string)) // "Swift.String"
String(reflecting: type(of: stringArray)) // "Swift.Array<Swift.String>"
String(reflecting: type(of: dictionary)) // "Swift.Dictionary<Swift.String, Swift.Int>"
其他回答
上面的答案没有使用type(of:的新方法的工作示例。所以为了帮助像我这样的新手，这里有一个工作的例子，主要来自苹果的文档- https://developer.apple.com/documentation/swift/2885064-type
doubleNum = 30.1
func printInfo(_ value: Any) {
let varType = type(of: value)
print("'\(value)' of type '\(varType)'")
}
printInfo(doubleNum)
//'30.1' of type 'Double'
不完全是你想要的，但你也可以检查Swift类型的变量类型，像这样:
let object: AnyObject = 1
if object is Int {
}
else if object is String {
}
为例。
从Xcode 6.3到Swift 1.2，你可以简单地将类型值转换为完整的需求型字符串。
toString(Int) // "Swift.Int"
toString(Int.Type) // "Swift.Int.Type"
toString((10).dynamicType) // "Swift.Int"
println(Bool.self) // "Swift.Bool"
println([UTF8].self) // "Swift.Array<Swift.UTF8>"
println((Int, String).self) // "(Swift.Int, Swift.String)"
println((String?()).dynamicType)// "Swift.Optional<Swift.String>"
println(NSDate) // "NSDate"
println(NSDate.Type) // "NSDate.Type"
println(WKWebView) // "WKWebView"
toString(MyClass) // "[Module Name].MyClass"
toString(MyClass().dynamicType) // "[Module Name].MyClass"
Xcode 8 Swift 3.0使用类型:
let className = "\(type(of: instance))"
在Swift 3.0中，你可以使用type(of:)，因为dynamicType关键字已被删除。
