How do I print the type or class of a variable in Swift?

Question

Is there a way to print the runtime type of a variable in swift? For example:

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

In the example above, I'm looking for a way to show that the variable "soon" is of type ImplicitlyUnwrappedOptional<NSDate>, or at least NSDate!.

Answer 1

Update September 2016

Swift 3.0: Use type(of:), e.g. type(of: someThing) (since the dynamicType keyword has been removed)

Update October 2015:

I updated the examples below to the new Swift 2.0 syntax (e.g. println was replaced with print, toString() is now String()).

From the Xcode 6.3 release notes:

@nschum points out in the comments that the Xcode 6.3 release notes show another way:

Type values now print as the full demangled type name when used with println or string interpolation.

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)")

Which outputs:

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>

Update for Xcode 6.3:

You can use the _stdlib_getDemangledTypeName():

print( "TypeName0 = \(_stdlib_getDemangledTypeName(myvar0))")
print( "TypeName1 = \(_stdlib_getDemangledTypeName(myvar1))")
print( "TypeName2 = \(_stdlib_getDemangledTypeName(myvar2))")
print( "TypeName3 = \(_stdlib_getDemangledTypeName(myvar3))")

and get this as output:

TypeName0 = NSString
TypeName1 = __lldb_expr_26.PureSwiftClass
TypeName2 = Swift.Int
TypeName3 = Swift.String

Original answer:

Prior to Xcode 6.3 _stdlib_getTypeName got the mangled type name of a variable. Ewan Swick's blog entry helps to decipher these strings:

e.g. _TtSi stands for Swift's internal Int type.

Mike Ash has a great blog entry covering the same topic.

Answer 2

Edit: A new toString function has been introduced in Swift 1.2 (Xcode 6.3).

You can now print the demangled type of any type using .self and any instance using .dynamicType:

struct Box<T> {}

toString("foo".dynamicType)            // Swift.String
toString([1, 23, 456].dynamicType)     // Swift.Array<Swift.Int>
toString((7 as NSNumber).dynamicType)  // __NSCFNumber

toString((Bool?).self)                 // Swift.Optional<Swift.Bool>
toString(Box<SinkOf<Character>>.self)  // __lldb_expr_1.Box<Swift.SinkOf<Swift.Character>>
toString(NSStream.self)                // NSStream

---

Try calling YourClass.self and yourObject.dynamicType.

Reference: https://devforums.apple.com/thread/227425.

Answer 3

Swift 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>"

Answer 4

Is this what you're looking for?

println("\(object_getClassName(now))");

It prints "__NSDate"

UPDATE: Please note this no longer seems to work as of Beta05

Answer 5

My current Xcode is Version 6.0 (6A280e).

import Foundation

class Person { var name: String; init(name: String) { self.name = name }}
class Patient: Person {}
class Doctor: Person {}

var variables:[Any] = [
    5,
    7.5,
    true,
    "maple",
    Person(name:"Sarah"),
    Patient(name:"Pat"),
    Doctor(name:"Sandy")
]

for variable in variables {
    let typeLongName = _stdlib_getDemangledTypeName(variable)
    let tokens = split(typeLongName, { $0 == "." })
    if let typeName = tokens.last {
        println("Variable \(variable) is of Type \(typeName).")
    }
}

Output:

Variable 5 is of Type Int.
Variable 7.5 is of Type Double.
Variable true is of Type Bool.
Variable maple is of Type String.
Variable Swift001.Person is of Type Person.
Variable Swift001.Patient is of Type Patient.
Variable Swift001.Doctor is of Type Doctor.

Answer 6

As of Xcode 6.3 with Swift 1.2, you can simply convert type values into the full demangled String.

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"

Answer 7

You can still access the class, through className (which returns a String).

There are actually several ways to get the class, for example classForArchiver, classForCoder, classForKeyedArchiver (all return AnyClass!).

You can't get the type of a primitive (a primitive is not a class).

Example:

var ivar = [:]
ivar.className // __NSDictionaryI

var i = 1
i.className // error: 'Int' does not have a member named 'className'

If you want to get the type of a primitive, you have to use bridgeToObjectiveC(). Example:

var i = 1
i.bridgeToObjectiveC().className // __NSCFNumber

Answer 8

You can use reflect to get information about object.
For example name of object class:

var classname = reflect(now).summary

Answer 9

Xcode 8 Swift 3.0 use type(of:)

let className = "\(type(of: instance))"

Answer 10

I had luck with:

let className = NSStringFromClass(obj.dynamicType)

Answer 11

SWIFT 5

With the latest release of Swift 3 we can get pretty descriptions of type names through the String initializer. Like, for example print(String(describing: type(of: object))). Where object can be an instance variable like array, a dictionary, an Int, a NSDate, an instance of a custom class, etc.

Here is my complete answer: Get class name of object as string in Swift

That question is looking for a way to getting the class name of an object as string but, also i proposed another way to getting the class name of a variable that isn't subclass of NSObject. Here it is:

class Utility{
    class func classNameAsString(obj: Any) -> String {
        //prints more readable results for dictionaries, arrays, Int, etc
        return String(describing: type(of: obj))
    }
}

I made a static function which takes as parameter an object of type Any and returns its class name as String :) .

I tested this function with some variables like:

    let diccionary: [String: CGFloat] = [:]
    let array: [Int] = []
    let numInt = 9
    let numFloat: CGFloat = 3.0
    let numDouble: Double = 1.0
    let classOne = ClassOne()
    let classTwo: ClassTwo? = ClassTwo()
    let now = NSDate()
    let lbl = UILabel()

and the output was:

• diccionary is of type Dictionary
• array is of type Array
• numInt is of type Int
• numFloat is of type CGFloat
• numDouble is of type Double
• classOne is of type: ClassOne
• classTwo is of type: ClassTwo
• now is of type: Date
• lbl is of type: UILabel

Answer 12

In Xcode 8, Swift 3.0

Steps:

1. Get the Type:

Option 1:

let type : Type = MyClass.self  //Determines Type from Class

Option 2:

let type : Type = type(of:self) //Determines Type from self

2. Convert Type to String:

let string : String = "\(type)" //String

Answer 13

In Swift 3.0, you can use type(of:), as dynamicType keyword has been removed.

Answer 14

To get a type of object or class of object in Swift, you must need to use a type(of: yourObject)

type(of: yourObject)

Answer 15

When using Cocoa (not CocoaTouch), you can use the className property for objects that are subclasses of NSObject.

println(now.className)

This property is not available for normal Swift objects, which aren't subclasses of NSObject (and in fact, there is no root id or object type in Swift).

class Person {
    var name: String?
}

var p = Person()
println(person.className) // <- Compiler error

In CocoaTouch, at this time there is not a way to get a string description of the type of a given variable. Similar functionality also does not exist for primitive types in either Cocoa or CocoaTouch.

The Swift REPL is able to print out a summary of values including its type, so it is possible this manner of introspection will be possible via an API in the future.

EDIT: dump(object) seems to do the trick.

Answer 16

The top answer doesn't have a working example of the new way of doing this using type(of:. So to help rookies like me, here is a working example, taken mostly from Apple's docs here - 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'

Answer 17

I've tried some of the other answers here but milage seems to very on what the underling object is.

However I did found a way you can get the Object-C class name for an object by doing the following:

now?.superclass as AnyObject! //replace now with the object you are trying to get the class name for

Here is and example of how you would use it:

let now = NSDate()
println("what is this = \(now?.superclass as AnyObject!)")

In this case it will print NSDate in the console.

Answer 18

I found this solution which hopefully might work for someone else. I created a class method to access the value. Please bear in mind this will work for NSObject subclass only. But at least is a clean and tidy solution.

class var className: String!{
    let classString : String = NSStringFromClass(self.classForCoder())
    return classString.componentsSeparatedByString(".").last;
}

Answer 19

In the latest XCode 6.3 with Swift 1.2, this is the only way I found:

if view.classForCoder.description() == "UISegment" {
    ...
}

Answer 20

Many of the answers here do not work with the latest Swift (Xcode 7.1.1 at time of writing).

The current way of getting the information is to create a Mirror and interrogate that. For the classname it is as simple as:

let mirror = Mirror(reflecting: instanceToInspect)
let classname:String = mirror.description

Additional information about the object can also be retrieved from the Mirror. See http://swiftdoc.org/v2.1/type/Mirror/ for details.

Answer 21

Swift version 4:

print("\(type(of: self)) ,\(#function)")
// within a function of a class

Thanks @Joshua Dance

Answer 22

Swift 4:

// "TypeName"
func stringType(of some: Any) -> String {
    let string = (some is Any.Type) ? String(describing: some) : String(describing: type(of: some))
    return string
}

// "ModuleName.TypeName"
func fullStringType(of some: Any) -> String {
    let string = (some is Any.Type) ? String(reflecting: some) : String(reflecting: type(of: some))
    return string
}

Usage:

print(stringType(of: SomeClass()))     // "SomeClass"
print(stringType(of: SomeClass.self))  // "SomeClass"
print(stringType(of: String()))        // "String"
print(fullStringType(of: String()))    // "Swift.String"

Answer 23

In lldb as of beta 5, you can see the class of an object with the command:

fr v -d r shipDate

which outputs something like:

(DBSalesOrderShipDate_DBSalesOrderShipDate_ *) shipDate = 0x7f859940

The command expanded out means something like:

Frame Variable (print a frame variable) -d run_target (expand dynamic types)

Something useful to know is that using "Frame Variable" to output variable values guarantees no code is executed.

Answer 24

I've found a solution for self-developed classes (or such you have access to).

Place the following computed property within your objects class definition:

var className: String? {
    return __FILE__.lastPathComponent.stringByDeletingPathExtension
}

Now you can simply call the class name on your object like so:

myObject.className

Please note that this will only work if your class definition is made within a file that is named exactly like the class you want the name of.

As this is commonly the case the above answer should do it for most cases. But in some special cases you might need to figure out a different solution.

---

If you need the class name within the class (file) itself you can simply use this line:

let className = __FILE__.lastPathComponent.stringByDeletingPathExtension

---

Maybe this method helps some people out there.

Answer 25

Based on the answers and comments given by Klass and Kevin Ballard above, I would go with:

println(_stdlib_getDemangledTypeName(now).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(soon).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(soon?).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(soon!).componentsSeparatedByString(".").last!)

println(_stdlib_getDemangledTypeName(myvar0).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(myvar1).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(myvar2).componentsSeparatedByString(".").last!)
println(_stdlib_getDemangledTypeName(myvar3).componentsSeparatedByString(".").last!)

which will print out:

"NSDate"
"ImplicitlyUnwrappedOptional"
"Optional"
"NSDate"

"NSString"
"PureSwiftClass"
"Int"
"Double"

Answer 26

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)")

Answer 27

There appears to be no generic way to print the type name of an arbitrary value's type. As others have noted, for class instances you can print value.className but for primitive values it appears that at runtime, the type information is gone.

For instance, it looks as if there's not a way to type: 1.something() and get out Int for any value of something. (You can, as another answer suggested, use i.bridgeToObjectiveC().className to give you a hint, but __NSCFNumber is not actually the type of i -- just what it will be converted to when it crosses the boundary of an Objective-C function call.)

I would be happy to be proven wrong, but it looks like the type checking is all done at compile time, and like C++ (with RTTI disabled) much of the type information is gone at runtime.

Answer 28

This is how you get a type string of your object or Type which is consistent and takes into account to which module the object definition belongs to or nested in. Works in Swift 4.x.

@inline(__always) func typeString(for _type: Any.Type) -> String {
    return String(reflecting: type(of: _type))
}

@inline(__always) func typeString(for object: Any) -> String {
    return String(reflecting: type(of: type(of: object)))
}

struct Lol {
    struct Kek {}
}

// if you run this in playground the results will be something like
typeString(for: Lol.self)    //    __lldb_expr_74.Lol.Type
typeString(for: Lol())       //    __lldb_expr_74.Lol.Type
typeString(for: Lol.Kek.self)//    __lldb_expr_74.Lol.Kek.Type
typeString(for: Lol.Kek())   //    __lldb_expr_74.Lol.Kek.Type

Answer 29

Not exactly what you are after, but you can also check the type of the variable against Swift types like so:

let object: AnyObject = 1

if object is Int {
}
else if object is String {
}

For example.

Answer 30

Xcode 7.3.1, Swift 2.2:

String(instanceToPrint.self).componentsSeparatedByString(".").last

Answer 31

Swift 3.0, Xcode 8

With the following code you can ask an instance for its class. You can also compare two instances, wether having the same class.

// 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")
}

Answer 32

This is also handy when checking if an object is a type of a class:

if someObject is SomeClass {
    //someObject is a type of SomeClass
}

Answer 33

Please have a look at the below code snippet and let me know if you are looking for something like below or not.

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)")

Answer 34

Another important aspect that influences the class name returned from String(describing: type(of: self)) is Access Control.

Consider the following example, based on Swift 3.1.1, Xcode 8.3.3 (July 2017)

func printClassNames() {

    let className1 = SystemCall<String>().getClassName()
    print(className1) // prints: "SystemCall<String>"

    let className2 = DemoSystemCall().getClassName()
    print(className2) // prints: "DemoSystemCall"

    // private class example
    let className3 = PrivateDemoSystemCall().getClassName()
    print(className3) // prints: "(PrivateDemoSystemCall in _0FC31E1D2F85930208C245DE32035247)" 

    // fileprivate class example
    let className4 = FileprivateDemoSystemCall().getClassName()
    print(className4) // prints: "(FileprivateDemoSystemCall in _0FC31E1D2F85930208C245DE32035247)" 
}

class SystemCall<T> {
    func getClassName() -> String {
        return String(describing: type(of: self))
    }
}

class DemoSystemCall: SystemCall<String> { }

private class PrivateDemoSystemCall: SystemCall<String> { }

fileprivate class FileprivateDemoSystemCall: SystemCall<String> { }

As you can see, all classes in this example have different levels of access control which influence their String representation. In case the classes have private or fileprivate access control levels, Swift seems to append some kind of identifier related to the "nesting" class of the class in question.

The result for both PrivateDemoSystemCall and FileprivateDemoSystemCall is that the same identifier is appended because they both are nested in the same parent class.

I have not yet found a way to get rid of that, other than some hacky replace or regex function.

Just my 2 cents.