How to successfully compile NSClassFromString in Swift - swift

Question

Code below can't compile successfully.I also attached a screenshot for reference!
func getXibViewWithClassNameString(classNameString:String)->AnyObject?{
let projectName = Bundle.main.infoDictionary!["CFBundleExecutable"] as? String
let MyClass:AnyClass = NSClassFromString(projectName! + "." + classNameString)!
var viewArray:NSArray?
var xibView:AnyClass?
Bundle.main.loadNibNamed(classNameString, owner: nil, topLevelObjects: &viewArray)
for viewInArray in viewArray ?? [] {
if (viewInArray is MyClass){
xibView = viewInArray as MyClass
}
}
return xibView
}
screenshot for reference

Answer 1

The key mistake here is that you can't as or is check on a dynamic type. You need to have a static type, known at compile time, to use that. As pointum notes, you need to use isKind(of:) or isMember(of:) on the underlying NSObject instead. Here's how I would recommend doing that:
func firstXibViewOfClass(named classNameString: String) -> NSView? {
// Create an AnyClass object
guard let projectName = Bundle.main.infoDictionary?["CFBundleExecutable"] as? String,
let myClass = NSClassFromString(projectName + "." + classNameString)
else {
return nil
}
// Load the nib
var topLevelObjects: NSArray?
Bundle.main.loadNibNamed(classNameString, owner: nil, topLevelObjects: &topLevelObjects)
// Convert it to NSObjects (since they all are going to be)
guard let nsObjectArray = topLevelObjects as? [NSObject] else { return nil }
// Find the first matching view and return it as an NSView if possible
return nsObjectArray.first(where: {
$0.isKind(of: myClass) // Or isMember(of:) if you want to be strict
}) as? NSView
}
If you don't need to include subclasses, though, you might want to just check the classname directly. This gets rid of all the AnyClass stuff:
func firstXibViewOfClass(named classNameString: String) -> NSView? {
// Load the nib
var topLevelObjects: NSArray?
Bundle.main.loadNibNamed(classNameString, owner: nil, topLevelObjects: &topLevelObjects)
// Convert it to NSObjects (since they all are going to be)
guard let nsObjectArray = topLevelObjects as? [NSObject] else { return nil }
// Find the first matching view and return it as an NSView if possible
return nsObjectArray.first(where: { $0.className == classNameString }) as? NSView
}
You could of course just return AnyObject?, but the name of the method suggests that you expect it to be a view, so you should enforce that or rename the method.

Answer 2

You can test with
if viewInArray.isKind(of: MyClass) { ... }
or
if viewInArray.isMember(of: MyClass) { ... } // strict class match
But I don’t think you can cast to a class that is not available at compile time to Swift. You won’t be able to directly call any of its methods anyway. You can cast it to some NSObject subclass and send arbitrary (not defined at compile time) messages to it, though.