CODEWITHSUNDEEP
swift
drinking
drinking

Reputation: 1553

How to convert AnyClass to a specific Class and init it dynamically in Swift?

In Object-C I store Class objects in an array and init them dynamically like this:

self.controllers=@[[OneViewController class],[TwoViewController class]];
Class clz = self.controllers[index];
UIViewController *detailViewController = [[clz alloc] init];

In Swift i try this way but it raises an error:

var controllers:AnyClass[] = [OneViewController.self,TwoViewController.self]
var clz : AnyClass = controllers[index]
var instance = clz() // Error:'AnyObject' is not constructible with ()

I wonder Whether there is a way to convert AnyClass to a specific Class? Or any other good ideas?

Upvotes: 53

Views: 34513

Answers (5)

Sentry.co
Sentry.co

Reputation: 5569

Here is a pure swift implementation of dynamic class types. It does require the classes to extend the same protocol.

protocol ILayout { init(_ a:S tring) }   
class A: ILayout { required init(_ a: String) }  
class B: ILayout { required init(_ a:String) }   
var instance: ILayout   
var classType: ILayout.Type

classType = A.self   
instance = classType.init("abc")

classType = B.self   
instance = classType.init("abc")

Upvotes: 8

DarkDust
DarkDust

Reputation: 92335

You can specify the array to be of the common superclass' type, then type deduction does the right thing (Beta-3 syntax):

let classArray: [UIViewController.Type] = [
    OneViewController.self, TwoViewController.self
]
let controllerClass = classArray[index]
let controller = controllerClass.init()

Upvotes: 56

Maic López Sáenz
Maic López Sáenz

Reputation: 10901

An AnyClass variable must first be casted into a specific type in order to initialize an instance:

// Code checked to run on xCode 7.1.1
import UIKit

var aClass: AnyClass = UIButton.self

// Error: 'init' is a member of the type...
// let doesNotWork = aClass.init()

// aClass must be casted first
var buttonClass = aClass as! UIButton.Type
var oneButton = buttonClass!.init()
var otherButton = buttonClass!.init(frame: CGRectZero)

Upvotes: 12

Xianng
Xianng

Reputation: 332

i have found a way to solve this problem:

var controllers:AnyClass[] = [OneViewController.self,TwoViewController.self]
var clz: NSObject.Type = controllers[0] as NSObject.Type
var con = clz()

remember to add @objc in the class of ViewController

Upvotes: 12

marcprux
marcprux

Reputation: 10355

If the classes are all Objective-C NSObject subclasses, you can do something like this (yes, the backticks are intentional):

var constructors: (Void -> NSObject!)[] = [ NSMutableString.`new`, NSMutableArray.`new`, NSMutableDictionary.`new` ]

let string = constructors[0]()
(string as NSMutableString).appendString("Hello")

let array = constructors[1]()
(array as NSMutableArray).addObject("Swift")

let dictionary = constructors[2]()
(dictionary as NSMutableDictionary).setObject("Objective-C", forKey: "Goodbye")

NSLog("dynamically created a string: \(string), an array: \(array), and a dictionary: \(dictionary)")

It should output:

dynamically created a string: Hello, an array: (
    Swift
), and a dictionary: {
    Goodbye = "Objective-C";
}

It does seem to me that there should be a more elegant way to do this.

Upvotes: 0

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