How to Obtain a Swift Type from a String

Is it possible to obtain a Swift type from a string?

No, it's not possible yet (as a language feature, at least).

What you need is your own type registry. Even with a type registry, you wouldn't be able to get static constants unless you had a protocol for that:

var typeRegistry: [String: Any.Type] = [:]

func indexType(type: Any.Type)
{
    typeRegistry[String(type)] = type
}

protocol Foo
{
    static var bar: String { get set }
}

struct X: Foo
{
    static var bar: String = "x-bar"
}

struct Y: Foo
{
    static var bar: String = "y-bar"
}

indexType(X)
indexType(Y)

typeRegistry // ["X": X.Type, "Y": Y.Type]

(typeRegistry["X"] as! Foo.Type).bar // "x-bar"
(typeRegistry["Y"] as! Foo.Type).bar // "y-bar"

A type registry is something that registers your types using a custom Hashable type (say a String or an Int). You can then use this type registry to reference registered types using custom identifiers (a String, in this case).

Since Any.Type by itself isn't all that useful, I constructed an interface Foo through which I could access a static constant bar. Because I know that X.Type and Y.Type both conform to Foo.Type, I forced a cast and read the bar property.

How to create an instance of a class from a String in Swift

You can try this:

func classFromString(_ className: String) -> AnyClass! {

    /// get namespace
    let namespace = Bundle.main.infoDictionary!["CFBundleExecutable"] as! String

    /// get 'anyClass' with classname and namespace 
    let cls: AnyClass = NSClassFromString("\(namespace).\(className)")!

    // return AnyClass!
    return cls
}

use the func like this:

class customClass: UITableView {}   

let myclass = classFromString("customClass") as! UITableView.Type
let instance = myclass.init()

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

Swift 3 version:

type(of: yourObject)

How to get a Swift type name as a string with its namespace (or framework name)

Use String(reflecting:):

struct Bar { }

let barName = String(reflecting: Bar.self) 
print(barName) // <Module>.Bar

From the Xcode 7 Release Notes:

Type names and enum cases now print and convert to String without
qualification by default. debugPrint or String(reflecting:) can still
be used to get fully qualified names.

Get the name (string) of a generic type in Swift

A pure swift way to achieve that is not possible.

A possible workaround is:

class MyClass<T: AnyObject> {
    func genericName() -> String {
        let fullName: String = NSStringFromClass(T.self)
        let range = fullName.rangeOfString(".", options: .BackwardsSearch)
        if let range = range {
            return fullName.substringFromIndex(range.endIndex)
        } else {
            return fullName
        }
    }
}

The limitations relies on the fact that it works with classes only.

If this is the generic type:

class TestClass {}

NSStringFromClass() returns the full name (including namespace):

// Prints something like "__lldb_expr_186.TestClass" in playground
NSStringFromClass(TestClass.self)

That's why the func searches for the last occurrence of the . character.

Tested as follows:

var x = MyClass<TestClass>()
x.genericName() // Prints "TestClass"

UPDATE Swift 3.0

func genericName() -> String {
    let fullName: String = NSStringFromClass(T.self)
    let range = fullName.range(of: ".")
    if let range = range {
        return fullName.substring(from: range.upperBound)
    }
    return fullName
}

How to convert a string with the name of a class to the class type itself?

You can get your class back from string, but you need to use your project's module name while getting class name. If you don't use your module name then it will return nil because the class name you have referenced earlier is not fully qualified by the module name. You should change the class name string to represent the fully qualified name of your class:

let myClassString = String(MyModule.MyViewController.self)
print(myClassString)
let myClass = NSClassFromString("MyModule.\(myClassString)") as! MyViewController.Type
print(myClass)

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

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.

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