How to create an object depending on a String in Swift?

Question

Here is my code what I would like to refactor:

let myCell = MyCustomTableViewCell()
self.createCell(myCell, reuseIdentifierString: "myCellIdentifier")

the MyCustomTableViewCell conforms to the SetCell protocol so it works fine. and the SetCell protocol is not an @obj_c protocol. This is a swift protocol

private func createCell<T where T:SetCell>(classType: T, reuseIdentifierString: String) -> UITableViewCell {
  var cell = _tableView.dequeueReusableCellWithIdentifier(reuseIdentifierString) as T
  cell.setText()
  return cell.getCustomCell()
}

And now I refactor my code, I would like to create the myCell depending on a String, but the string is exactly the same as my Class name. I dont want to use else-if or switch-case

let myCell: AnyClass! = NSClassFromString("MyCustomTableViewCell")
self.createCell(myCell, reuseIdentifierString: "myCellIdentifier")

But now the myCell which is AnyClass does not conform to protocol. How can I do this?

Edwin Vermeer · Accepted Answer · 2014-09-09T20:25:53.137

6

You need a little more code than that. You will get an AnyClass and not an AnyObject. So you need to create an instance of that type. You could try this:

let cellClass: AnyClass! = NSClassFromString("MyCell")
var objectType : NSObject.Type! = cellClass as NSObject.Type!
var theObject: NSObject! = objectType() as NSObject
var myCell:MyCell = theObject as MyCell

For letting it conform to your protocol you could try a couple of things:

1. You could create a base class for all your cells that conforms to a protocol. And use that in the code above instead of the UITableViewCell. For this you could use code like this:

protocol SetCell {
    func setcell() {}
}
class BaseUITableViewCell : UITableViewCell, SetCell {
    func setcell() {}
}
class MyCell : BaseUITableViewCell {
    override func setcell() {}
}

let cellClass: AnyClass! = NSClassFromString("MyCell")
var objectType : NSObject.Type! = cellClass as NSObject.Type!
var theObject: NSObject! = objectType() as NSObject
var myCell:BaseUITableViewCell = theObject as BaseUITableViewCell

2. You can extend the UITableViewCell with your extension like by adding an empty extension

extension UITableViewCell: SetCell {}

//compile-time error:

Declarations from extensions cannot be overridden yet

//Edwin: Strange, this is in the documentation. So it looks like this one is out...

3. You could define a variable that conforms to a protocol like this:

@objc protocol SetCell {
    func setcell() {}
}

let cellClass: AnyClass! = NSClassFromString("MyCell")
var objectType : NSObject.Type! = cellClass as NSObject.Type!
var myCell2:protocol<SetCell> = objectType() as protocol<SetCell>

edited Sep 09 '14 at 20:25

answered Sep 08 '14 at 17:52

Edwin Vermeer

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thanks Edwin. But where to define that myCell conforms to SetCell protocol? – szuniverse Sep 08 '14 at 18:27
Ah, sorry, I missed that part of your question. I will update my awnser – Edwin Vermeer Sep 08 '14 at 18:37
1

if you're going to do that, you might as well cast `cellClass` directly to `UITableViewCell.Type` – newacct Sep 08 '14 at 18:49
you are right newacct. The code above was a snippet out of a project of mine that was creating classes with NSObject as a base class. I updated the code – Edwin Vermeer Sep 08 '14 at 18:55
I updated your comment what I get when I try to implement it. Please see it, thanks in advance Edwin – szuniverse Sep 09 '14 at 15:53
OK, i have updated the answer again. You need to first create a NSObject type and then cast it to a MyCell. For the 3rd option, you need to add the @objc declaration to the class. Indeed it seems like the 2nd solution doesn't work anymore. Strange... It was in the documentation. – Edwin Vermeer Sep 09 '14 at 20:22
I modified your code please see it, thanks in advance – szuniverse Sep 10 '14 at 14:20

score 0 · Answer 2 · answered Mar 11 '16 at 07:14

class IndexViewController: UIViewController{}

let className = "IndexViewController"

let bundlePath = NSBundle.mainBundle().bundlePath
let bundleFullName = bundlePath.componentsSeparatedByString("/").last
let bundleName = bundleFullName?.componentsSeparatedByString(".").first
let clazz = NSClassFromString(bundleName! + "." + className)! as! UIViewController.Type
let object = clazz.init()
// let object1 = Index()

How to create an object depending on a String in Swift?

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