CODEWITHSUNDEEP
swifttypes
Matt Bridges
Matt Bridges

Reputation: 49435

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

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!.

Upvotes: 367

Views: 269658

Answers (30)

mauricioconde
mauricioconde

Reputation: 5142

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

Upvotes: 12

Desmond Hume
Desmond Hume

Reputation: 8627

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"

Upvotes: 4

Rahul Panzade
Rahul Panzade

Reputation: 1372

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

type(of: yourObject)

Upvotes: 7

Igor Muzyka
Igor Muzyka

Reputation: 409

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

Upvotes: 2

dengApro
dengApro

Reputation: 4038

Swift version 4:

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

Thanks @Joshua Dance

Upvotes: 4

Joshua Dance
Joshua Dance

Reputation: 10512

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'

Upvotes: 5

Philipp Jahoda
Philipp Jahoda

Reputation: 51421

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.

Upvotes: 0

DILIP KOSURI
DILIP KOSURI

Reputation: 465

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)")

Upvotes: 0

LukeSideWalker
LukeSideWalker

Reputation: 7930

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")
}

Upvotes: 1

Nam
Nam

Reputation: 1876

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
}

Upvotes: 0

Evgenii
Evgenii

Reputation: 37349

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>"

Upvotes: 41

Klaas
Klaas

Reputation: 22773

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.

Upvotes: 408

user1046037
user1046037

Reputation: 17725

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

Upvotes: 10

Hari Kunwar
Hari Kunwar

Reputation: 1681

Xcode 8 Swift 3.0 use type(of:)

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

Upvotes: 15

Bruno Serrano
Bruno Serrano

Reputation: 565

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

Upvotes: 9

leanne
leanne

Reputation: 8749

Xcode 7.3.1, Swift 2.2:

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

Upvotes: 1

Joseph Lord
Joseph Lord

Reputation: 6504

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.

Upvotes: 4

akashivskyy
akashivskyy

Reputation: 45210

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.

Upvotes: 46

PersuitOfPerfection
PersuitOfPerfection

Reputation: 1029

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.

Upvotes: 1

Joel Kopelioff
Joel Kopelioff

Reputation: 167

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

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

Upvotes: 4

kiding
kiding

Reputation: 1935

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"

Upvotes: 18

DennyLou
DennyLou

Reputation: 313

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;
}

Upvotes: 4

Alex Burla
Alex Burla

Reputation: 31

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)")

Upvotes: 3

Vince O&#39;Sullivan
Vince O&#39;Sullivan

Reputation: 2701

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"

Upvotes: 3

Cihat G&#252;nd&#252;z
Cihat G&#252;nd&#252;z

Reputation: 21478

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.

Upvotes: 3

James Jones
James Jones

Reputation: 1506

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.

Upvotes: 4

Matt Hagen
Matt Hagen

Reputation: 651

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.

Upvotes: 23

mxcl
mxcl

Reputation: 26903

I had luck with:

let className = NSStringFromClass(obj.dynamicType)

Upvotes: 13

Haiku Oezu
Haiku Oezu

Reputation: 897

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

Upvotes: 30

Kendall Helmstetter Gelner
Kendall Helmstetter Gelner

Reputation: 75057

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.

Upvotes: 3

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