How do you find out the type of an object (in Swif

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 :)

Answer 1

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 <ClassName> {
    //the variable is of type <ClassName>
} else {
    //variable is not of type <ClassName>
}

This is equivalent of isKindOfClass in Obj-C.

And this is equivalent of conformsToProtocol, or isMemberOfClass

var unknownTypeVariable = …

if let myClass = unknownTypeVariable as? <ClassName or ProtocolName> {
    //unknownTypeVarible is of type <ClassName or ProtocolName>
} else {
    //unknownTypeVariable is not of type <ClassName or ProtocolName>
}

Answer 2

//: 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

Answer 3

Swift 3 version:

type(of: yourObject)

Answer 4

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")
}

Answer 5

If you get an "always true/fails" warning you may need to cast to Any before using is

(foo as Any) is SomeClass

Answer 6

This works in swift 3

if unknownType is MyClass {
   //unknownType is of class type MyClass
}