Swift language NSClassFromString

How to achieve reflection in Swift Language?

How can I instantiate a class

[[NSClassFromString(@"Foo") alloc] init];

You must put @objc(SwiftClassName) above your swift class.
Like:

@objc(SubClass)
class SubClass: SuperClass {...}

This is the way I init derived UIViewController by class name

var className = "YourAppName.TestViewController"
let aClass = NSClassFromString(className) as! UIViewController.Type
let viewController = aClass()

More information is here

In iOS 9

var className = "YourAppName.TestViewController"
let aClass = NSClassFromString(className) as! UIViewController.Type
let viewController = aClass.init()

Less hacky solution here: https://stackoverflow.com/a/32265287/308315

Note that Swift classes are namespaced now so instead of "MyViewController" it'd be "AppName.MyViewController"

---

> Deprecated since XCode6-beta 6/7 > > Solution developed using XCode6-beta 3

Thanks to the answer of Edwin Vermeer I was able to build something to instantiate Swift classes into an Obj-C class by doing this:

// swift file
// extend the NSObject class
extension NSObject {
    // create a static method to get a swift class for a string name
    class func swiftClassFromString(className: String) -> AnyClass! {
        // get the project name
        if  var appName: String? = NSBundle.mainBundle().objectForInfoDictionaryKey("CFBundleName") as String? {
            // generate the full name of your class (take a look into your "YourProject-swift.h" file)
            let classStringName = "_TtC\(appName!.utf16count)\(appName)\(countElements(className))\(className)"
            // return the class!
            return NSClassFromString(classStringName)
        }
        return nil;
    }
}

// obj-c file
#import "YourProject-Swift.h"

- (void)aMethod {
    Class class = NSClassFromString(key);
    if (!class)
        class = [NSObject swiftClassFromString:(key)];
    // do something with the class
}

EDIT

You can also do it in pure obj-c:

- (Class)swiftClassFromString:(NSString *)className {
    NSString *appName = [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleName"];
    NSString *classStringName = [NSString stringWithFormat:@"_TtC%d%@%d%@", appName.length, appName, className.length, className];
    return NSClassFromString(classStringName);
}

I hope this will help somebody !

UPDATE: Starting with beta 6 NSStringFromClass will return your bundle name plus class name separated by a dot. So it will be something like MyApp.MyClass

Swift classes will have a constructed internal name that is build up of the following parts:

• It will start with _TtC,
• followed by a number that is the length of your application name,
• followed by your application name,
• folowed by a number that is the length of your class name,
• followed by your class name.

So your class name will be something like _TtC5MyApp7MyClass

You can get this name as a string by executing:

var classString = NSStringFromClass(self.dynamicType)

Update In Swift 3 this has changed to:

var classString = NSStringFromClass(type(of: self))

Using that string, you can create an instance of your Swift class by executing:

var anyobjectype : AnyObject.Type = NSClassFromString(classString)
var nsobjectype : NSObject.Type = anyobjectype as NSObject.Type
var rec: AnyObject = nsobjectype()

It's almost the same

func NSClassFromString(_ aClassName: String!) -> AnyClass!

Check this doc:

https://developer.apple.com/library/prerelease/ios/documentation/Cocoa/Reference/Foundation/Miscellaneous/Foundation_Functions/#//apple_ref/c/func/NSClassFromString

I was able to instantiate an object dynamically

var clazz: NSObject.Type = TestObject.self
var instance : NSObject = clazz()
    
if let testObject = instance as? TestObject {
    println("yes!")
}

I haven't found a way to create AnyClass from a String (without using Obj-C). I think they don't want you to do that because it basically breaks the type system.

For swift2, I created a very simple extension to do this more quickly https://github.com/damienromito/NSObject-FromClassName

extension NSObject {
    class func fromClassName(className : String) -> NSObject {
        let className = NSBundle.mainBundle().infoDictionary!["CFBundleName"] as! String + "." + className
        let aClass = NSClassFromString(className) as! UIViewController.Type
        return aClass.init()
    }
}

---

In my case, i do this to load the ViewController I want:

override func viewDidLoad() {
    super.viewDidLoad()
    let controllers = ["SettingsViewController", "ProfileViewController", "PlayerViewController"]
    self.presentController(controllers.firstObject as! String)

}

func presentController(controllerName : String){
    let nav = UINavigationController(rootViewController: NSObject.fromClassName(controllerName) as! UIViewController )
    nav.navigationBar.translucent = false
    self.navigationController?.presentViewController(nav, animated: true, completion: nil)
}

This will get you the name of the class that you want to instantiate. Then you can use Edwins answer to instantiate a new object of your class.

As of beta 6 _stdlib_getTypeName gets the mangled type name of a variable. Paste this into an empty playground:

import Foundation

class PureSwiftClass {
}

var myvar0 = NSString() // Objective-C class
var myvar1 = PureSwiftClass()
var myvar2 = 42
var myvar3 = "Hans"

println( "TypeName0 = \(_stdlib_getTypeName(myvar0))")
println( "TypeName1 = \(_stdlib_getTypeName(myvar1))")
println( "TypeName2 = \(_stdlib_getTypeName(myvar2))")
println( "TypeName3 = \(_stdlib_getTypeName(myvar3))")

The output is:

TypeName0 = NSString
TypeName1 = _TtC13__lldb_expr_014PureSwiftClass
TypeName2 = _TtSi
TypeName3 = _TtSS

Ewan Swick's blog entry helps to decipher these strings: http://www.eswick.com/2014/06/inside-swift/

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

In Swift 2.0 (tested in the Xcode 7.01) _20150930

let vcName =  "HomeTableViewController"
let ns = NSBundle.mainBundle().infoDictionary!["CFBundleExecutable"] as! String

// Convert string to class
let anyobjecType: AnyObject.Type = NSClassFromString(ns + "." + vcName)!
if anyobjecType is UIViewController.Type {
// vc is instance
    let vc = (anyobjecType as! UIViewController.Type).init()
    print(vc)
}

xcode 7 beta 5:

class MyClass {
    required init() { print("Hi!") }
}
if let classObject = NSClassFromString("YOURAPPNAME.MyClass") as? MyClass.Type {
    let object = classObject.init()
}

string from class

let classString = NSStringFromClass(TestViewController.self)

or

let classString = NSStringFromClass(TestViewController.classForCoder())

init a UIViewController class from string:

let vcClass = NSClassFromString(classString) as! UIViewController.Type
let viewController = vcClass.init()

I am using this category for Swift 3:

//
//  String+AnyClass.swift
//  Adminer
//
//  Created by Ondrej Rafaj on 14/07/2017.
//  Copyright © 2017 manGoweb UK Ltd. All rights reserved.
//

import Foundation


extension String {
    
    func convertToClass<T>() -> T.Type? {
        return StringClassConverter<T>.convert(string: self)
    }
    
}

class StringClassConverter<T> {
    
    static func convert(string className: String) -> T.Type? {
        guard let nameSpace = Bundle.main.infoDictionary?["CFBundleExecutable"] as? String else {
            return nil
        }
        guard let aClass: T.Type = NSClassFromString("\(nameSpace).\(className)") as? T.Type else {
            return nil
        }
        return aClass
        
    }
    
}

The use would be:

func getViewController(fromString: String) -> UIViewController? {
    guard let viewController: UIViewController.Type = "MyViewController".converToClass() else {
        return nil
    }
    return viewController.init()
}

I think I'm right in saying that you can't, at least not with the current beta (2). Hopefully this is something that will change in future versions.

You can use NSClassFromString to get a variable of type AnyClass but there appears to be no way in Swift to instantiate it. You can use a bridge to Objective C and do it there or -- if it works in your case -- fall back to using a switch statement.

Apparently, it is not possible (anymore) to instantiate an object in Swift when the name of the class is only known at runtime. An Objective-C wrapper is possible for subclasses of NSObject.

At least you can instantiate an object of the same class as another object given at runtime without an Objective-C wrapper (using xCode Version 6.2 - 6C107a):

    class Test : NSObject {}
    var test1 = Test()
    var test2 = test1.dynamicType.alloc()

In Swift 2.0 (tested in the beta2 of Xcode 7) it works like this:

protocol Init {
  init()
}

var type = NSClassFromString(className) as? Init.Type
let obj = type!.init()

For sure the type coming from NSClassFromString have to implement this init protocol.

I expect it is clear, className is a String containing the Obj-C runtime name of the class which is by default NOT just "Foo", but this discussion is IMHO not the major topic of your question.

You need this protocol because be default all Swift classes don't implement an init method.

Looks like the correct incantation would be...

func newForName<T:NSObject>(p:String) -> T? {
   var result:T? = nil

   if let k:AnyClass = NSClassFromString(p) {
      result = (k as! T).dynamicType.init()
   }

   return result
}

...where "p" stands for "packaged" – a distinct issue.

But the critical cast from AnyClass to T currently causes a compiler crash, so in the meantime one must bust initialization of k into a separate closure, which compiles fine.

I use different targets, and in this case the swift class is not found. You should replace CFBundleName with CFBundleExecutable. I also fixed the warnings:

- (Class)swiftClassFromString:(NSString *)className {
    NSString *appName = [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleExecutable"];
    NSString *classStringName = [NSString stringWithFormat:@"_TtC%lu%@%lu%@", (unsigned long)appName.length, appName, (unsigned long)className.length, className];
    return NSClassFromString(classStringName);
}

Isn't the solution as simple as this?

// Given the app/framework/module named 'MyApp'
let className = String(reflecting: MyClass.self)

// className = "MyApp.MyClass"

Also in Swift 2.0 (possibly before?) You can access the type directly with the dynamicType property

i.e.

class User {
    required init() { // class must have an explicit required init()
    }
    var name: String = ""
}
let aUser = User()
aUser.name = "Tom"
print(aUser)
let bUser = aUser.dynamicType.init()
print(bUser)

Output

aUser: User = {
  name = "Tom"
}
bUser: User = {
  name = ""
}

Works for my use case

Try this.

let className: String = String(ControllerName.classForCoder())
print(className)

I have implemented like this,

if let ImplementationClass: NSObject.Type = NSClassFromString(className) as? NSObject.Type{
   ImplementationClass.init()
}

Swift 5, easy to use, thanks to @Ondrej Rafaj's

• Source code:

   extension String {
        fileprivate
        func convertToClass<T>() -> T.Type? {
             return StringClassConverter<T>.convert(string: self)
        }
  
   
       var controller: UIViewController?{
             guard let viewController: UIViewController.Type = convertToClass() else {
               return nil
           }
           return viewController.init()
       }
   }
  
   class StringClassConverter<T> {
        fileprivate
        static func convert(string className: String) -> T.Type? {
            guard let nameSpace = Bundle.main.infoDictionary?["CFBundleExecutable"] as? String, let aClass = NSClassFromString("\(nameSpace).\(className)") as? T.Type else {
                return nil
           }
            return aClass
  
      }
  
   }
  

• Call like this:

   guard let ctrl = "ViewCtrl".controller else {
       return
   }
   //  ctrl do sth
  

A page jump example shown here, the hope can help you!

let vc:UIViewController = (NSClassFromString("SwiftAutoCellHeight."+type) as! UIViewController.Type).init()
self.navigationController?.pushViewController(vc, animated: true)

// Click the Table response
tableView.deselectRow(at: indexPath, animated: true)
let sectionModel = models[(indexPath as NSIndexPath).section]
var className = sectionModel.rowsTargetControlerNames[(indexPath as NSIndexPath).row]
className = "GTMRefreshDemo.\(className)"
if let cls = NSClassFromString(className) as? UIViewController.Type {
   let dvc = cls.init()
   self.navigationController?.pushViewController(dvc, animated: true)
}

Swift3+

extension String {
    
    var `class`: AnyClass? {
        
        guard
            let dict = Bundle.main.infoDictionary,
            var appName = dict["CFBundleName"] as? String
            else { return nil }
        
        appName.replacingOccurrences(of: " ", with: "_")
        let className = appName + "." + self
        return NSClassFromString(className)
    }
}

Here is a good example:

class EPRocks { 
    @require init() { } 
}

class EPAwesome : EPRocks { 
    func awesome() -> String { return "Yes"; } 
}

var epawesome = EPAwesome.self(); 
print(epawesome.awesome);