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
2016年9月更新
Swift 3.0:使用type(of:)，例如type(of: someThing)(因为dynamicType关键字已被删除)
2015年10月更新:
我更新了下面的例子到新的Swift 2.0语法(例如println替换为print, toString()现在是String())。
Xcode 6.3发布说明:
@nschum在评论中指出，Xcode 6.3发布说明显示了另一种方式:
使用时，类型值现在打印为完整的需求类型名 Println或字符串插值。
import Foundation
class PureSwiftClass { }
var myvar0 = NSString() // Objective-C class
var myvar1 = PureSwiftClass()
var myvar2 = 42
var myvar3 = "Hans"
print( "String(myvar0.dynamicType) -> \(myvar0.dynamicType)")
print( "String(myvar1.dynamicType) -> \(myvar1.dynamicType)")
print( "String(myvar2.dynamicType) -> \(myvar2.dynamicType)")
print( "String(myvar3.dynamicType) -> \(myvar3.dynamicType)")
print( "String(Int.self) -> \(Int.self)")
print( "String((Int?).self -> \((Int?).self)")
print( "String(NSString.self) -> \(NSString.self)")
print( "String(Array<String>.self) -> \(Array<String>.self)")
输出:
String(myvar0.dynamicType) -> __NSCFConstantString
String(myvar1.dynamicType) -> PureSwiftClass
String(myvar2.dynamicType) -> Int
String(myvar3.dynamicType) -> String
String(Int.self) -> Int
String((Int?).self -> Optional<Int>
String(NSString.self) -> NSString
String(Array<String>.self) -> Array<String>
Xcode 6.3更新:
你可以使用_stdlib_getDemangledTypeName():
print( "TypeName0 = \(_stdlib_getDemangledTypeName(myvar0))")
print( "TypeName1 = \(_stdlib_getDemangledTypeName(myvar1))")
print( "TypeName2 = \(_stdlib_getDemangledTypeName(myvar2))")
print( "TypeName3 = \(_stdlib_getDemangledTypeName(myvar3))")
并将其作为输出:
TypeName0 = NSString
TypeName1 = __lldb_expr_26.PureSwiftClass
TypeName2 = Swift.Int
TypeName3 = Swift.String
最初的回答:
在Xcode 6.3之前，_stdlib_getTypeName获取变量的类型名。伊万·斯维克(Ewan Swick)的博客有助于解读这些字符串:
例如:_TtSi代表Swift的内部Int类型。
Mike Ash有一篇很棒的博客文章涉及了同样的主题。
其他回答
在lldb beta 5中，你可以通过以下命令查看对象的类:
fr v -d r shipDate
输出如下:
(DBSalesOrderShipDate_DBSalesOrderShipDate_ *) shipDate = 0x7f859940
展开的命令是这样的:
帧变量(打印帧变量)-d run_target(展开动态类型)
需要知道的一点是，使用“Frame Variable”来输出变量值可以确保不执行任何代码。
2016年9月更新
Swift 3.0:使用type(of:)，例如type(of: someThing)(因为dynamicType关键字已被删除)
2015年10月更新:
我更新了下面的例子到新的Swift 2.0语法(例如println替换为print, toString()现在是String())。
Xcode 6.3发布说明:
@nschum在评论中指出，Xcode 6.3发布说明显示了另一种方式:
使用时，类型值现在打印为完整的需求类型名 Println或字符串插值。
import Foundation
class PureSwiftClass { }
var myvar0 = NSString() // Objective-C class
var myvar1 = PureSwiftClass()
var myvar2 = 42
var myvar3 = "Hans"
print( "String(myvar0.dynamicType) -> \(myvar0.dynamicType)")
print( "String(myvar1.dynamicType) -> \(myvar1.dynamicType)")
print( "String(myvar2.dynamicType) -> \(myvar2.dynamicType)")
print( "String(myvar3.dynamicType) -> \(myvar3.dynamicType)")
print( "String(Int.self) -> \(Int.self)")
print( "String((Int?).self -> \((Int?).self)")
print( "String(NSString.self) -> \(NSString.self)")
print( "String(Array<String>.self) -> \(Array<String>.self)")
输出:
String(myvar0.dynamicType) -> __NSCFConstantString
String(myvar1.dynamicType) -> PureSwiftClass
String(myvar2.dynamicType) -> Int
String(myvar3.dynamicType) -> String
String(Int.self) -> Int
String((Int?).self -> Optional<Int>
String(NSString.self) -> NSString
String(Array<String>.self) -> Array<String>
Xcode 6.3更新:
你可以使用_stdlib_getDemangledTypeName():
print( "TypeName0 = \(_stdlib_getDemangledTypeName(myvar0))")
print( "TypeName1 = \(_stdlib_getDemangledTypeName(myvar1))")
print( "TypeName2 = \(_stdlib_getDemangledTypeName(myvar2))")
print( "TypeName3 = \(_stdlib_getDemangledTypeName(myvar3))")
并将其作为输出:
TypeName0 = NSString
TypeName1 = __lldb_expr_26.PureSwiftClass
TypeName2 = Swift.Int
TypeName3 = Swift.String
最初的回答:
在Xcode 6.3之前，_stdlib_getTypeName获取变量的类型名。伊万·斯维克(Ewan Swick)的博客有助于解读这些字符串:
例如:_TtSi代表Swift的内部Int类型。
Mike Ash有一篇很棒的博客文章涉及了同样的主题。
请看看下面的代码片段，让我知道你是否在寻找下面这样的东西。
var now = NSDate()
var soon = now.addingTimeInterval(5.0)
var nowDataType = Mirror(reflecting: now)
print("Now is of type: \(nowDataType.subjectType)")
var soonDataType = Mirror(reflecting: soon)
print("Soon is of type: \(soonDataType.subjectType)")
Swift 3.0, Xcode 8
使用下面的代码，您可以向实例请求其类。你也可以比较两个实例，是否具有相同的类。
// CREATE pure SWIFT class
class MySwiftClass {
var someString : String = "default"
var someInt : Int = 5
}
// CREATE instances
let firstInstance = MySwiftClass()
let secondInstance = MySwiftClass()
secondInstance.someString = "Donald"
secondInstance.someInt = 24
// INSPECT instances
if type(of: firstInstance) === MySwiftClass.self {
print("SUCCESS with ===")
} else {
print("PROBLEM with ===")
}
if type(of: firstInstance) == MySwiftClass.self {
print("SUCCESS with ==")
} else {
print("PROBLEM with ==")
}
// COMPARE CLASS OF TWO INSTANCES
if type(of: firstInstance) === type(of: secondInstance) {
print("instances have equal class")
} else {
print("instances have NOT equal class")
}
let i: Int = 20
func getTypeName(v: Any) -> String {
let fullName = _stdlib_demangleName(_stdlib_getTypeName(i))
if let range = fullName.rangeOfString(".") {
return fullName.substringFromIndex(range.endIndex)
}
return fullName
}
println("Var type is \(getTypeName(i)) = \(i)")
