How do you find out the type of an object in Swift

Question

When trying to understand a program  or in some corner-cases  it s useful to be able to actually find out what type something is  I know the debugger can show you some type information  and you can usually rely on type inference to get away with not specifying the type in those situations  but still  I d really like to have something like Python s type    dynamicType  see this question   Update  this has been changed in a recent version of Swift  obj dynamicType now gives you a reference to the type and not the instance of the dynamic type   This one seems the most promising  but so far I haven t been able to find out the actual type  class MyClass       var count   0    let mc   MyClass      update  this now evaluates as true mc dynamicType     MyClass self   I also tried using a class reference to instantiate a new object  which does work  but oddly gave me an error saying I must add a required initializer   works   class MyClass       var count   0     required init              let myClass2   MyClass self let mc2   MyClass2     Still only a small step toward actually discovering the type of any given object though  edit  I ve removed a substantial number of now irrelevant details - look at the edit history if you re interested

User · Accepted Answer

Swift 3 version   type of  yourObject

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If you get an  always true fails  warning you may need to cast to Any before using is   foo as Any  is SomeClass

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Swift 2 0   The proper way to do this kind of type introspection would be with the Mirror struct        let stringObject String    testing      let stringArrayObject  String      one    two       let viewObject   UIView       let anyObject Any    testing       let stringMirror   Mirror reflecting  stringObject      let stringArrayMirror   Mirror reflecting  stringArrayObject      let viewMirror   Mirror reflecting  viewObject      let anyMirror   Mirror reflecting  anyObject    Then to access the type itself from the Mirror struct you would use the property subjectType like so          Prints  String      print stringMirror subjectType          Prints  Array lt String gt       print stringArrayMirror subjectType          Prints  UIView      print viewMirror subjectType          Prints  String      print anyMirror subjectType    You can then use something like this       if anyMirror subjectType    String self           print  anyObject is a string          else           print  anyObject is not a string

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Depends on the use case  But let s assume you want to do something useful with your  variable  types  The Swift switch statement is very powerful and can help you get the results you re looking for         let dd2     x    9   y     home9       let dds   dd2 filter           let eIndex    x          let eValue Any   9         var r   false          switch eValue           case let testString as String              r    1    testString         case let testUInt as UInt              r    1    testUInt         case let testInt as Int              r    1    testInt         default              r   false                    return r  amp  amp   0    eIndex         In this case   have a simple dictionary that contains key value pairs that can be UInt  Int or String  In the  filter   method on the dictionary  I need to make sure I test for the values correctly and only test for a String when it s a string  etc  The switch statement makes this simple and safe  By assigning 9 to the variable of type Any  it makes the switch for Int execute  Try changing it to      let eValue Any    home9      and try it again  This time it executes the as String case

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If you simply need to check whether the variable is of type X  or that it conforms to some protocol  then you can use is  or as  as in the following   var unknownTypeVariable        if unknownTypeVariable is  lt ClassName gt          the variable is of type  lt ClassName gt    else         variable is not of type  lt ClassName gt      This is equivalent of isKindOfClass in Obj-C   And this is equivalent of conformsToProtocol  or isMemberOfClass  var unknownTypeVariable        if let myClass   unknownTypeVariable as   lt ClassName or ProtocolName gt          unknownTypeVarible is of type  lt ClassName or ProtocolName gt    else         unknownTypeVariable is not of type  lt ClassName or ProtocolName gt

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The dynamicType printClassName code is from an example in the Swift book  There s no way I know of to directly grab a custom class name  but you can check an instances type using the is keyword as shown below  This example also shows how to implement a custom className function  if you really want the class name as a string   class Shape       class func className   - gt  String           return  Shape           class Square  Shape       override class func className   - gt  String           return  Square           class Circle  Shape       override class func className   - gt  String           return  Circle           func getShape   - gt  Shape       return Square      hardcoded for example    let newShape  Shape   getShape   newShape is Square    true newShape is Circle    false newShape dynamicType className       Square  newShape dynamicType className      Square className      true   Note  that subclasses of NSObject already implement their own className function  If you re working with Cocoa  you can just use this property   class MyObj  NSObject       init             super init           println  My class is   self className            MyObj

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Swift 3   if unknownType is MyClass        unknownType is of class type MyClass

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For Swift 3 0  String describing   lt Class-Name gt  self    For Swift 2 0 - 2 3  String  lt Class-Name gt

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Old question  but this works for my need  Swift 5 x   print type of  myObjectName

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Here is 2 ways I recommend doing it   if let thisShape   aShape as  Square    Or   aShape isKindOfClass Square    Here is a detailed example    class Shape     class Square  Shape      class Circle  Shape      var aShape   Shape   aShape   Square    if let thisShape   aShape as  Square       println  Its a square     else       println  Its not a square      if aShape isKindOfClass Square        println  Its a square     else       println  Its not a square

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Playground - noun  a place where people can play  import UIKit  class A       class func a             print  yeah              func getInnerValue             self dynamicType a            class B  A       override class func a             print  yeah yeah            B a      yeah yeah A a      yeah B   getInnerValue      yeah yeah A   getInnerValue      yeah

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As of Xcode 6 0 1  at least  not sure when they added it   your original example now works   class MyClass       var count   0    let mc   MyClass   mc dynamicType     MyClass self    returns  true    Update   To answer the original question  you can actually use the Objective-C runtime with plain Swift objects successfully   Try the following   import Foundation class MyClass     class SubClass  MyClass      let mc   MyClass   let m2   SubClass       Both of these return  Some    lldb expr 35 SubClass    which is the fully mangled class name from the playground String fromCString class getName m2 dynamicType   String fromCString object getClassName m2      Returns  Some    lldb expr 42 MyClass   String fromCString object getClassName mc

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If a parameter is passed as Any to your function  you can test on a special type like so      func isADate   aValue   Any   - gt  Bool          if  aValue as  Date     nil               print   quot a Date quot               return true                   else               print   quot This is not a date  quot               return false

[swift] How do you find out the type of an object (in Swift)?

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