swift setter causing exc_bad_access

Question

I have a simple class below

import Foundation

public class UsefulClass: NSObject{
    var test:NSNumber{
        get{return self.test}
        set{
                


        

Answer 1

It's an infinite loop; your setter is recursively calling itself.

var test: NSNumber {
    set {
        test = newValue
    }
}

This compiles fine, and an Objective-C programmer might expect no loop due to instead setting a "backing ivar" such as _test rather than re-calling the setter method.

But property-backing instance variable _ivars do not exist in Swift for computed properties unless you create them yourself.