Attempting to use the new block-based KVO in Xcode 9 and Swift 4

KVO.swift

//: Playground - noun: a place where people can play

import Foundation

class HelloThere: NSObject {
    
    @objc var value: String = ""
    
}

let object = HelloThere()

let observer = object.observe(\.value) { (object, change) in
    
    print("Changed to \(object.value)")
    
}

object.value = "1"
object.value = "2"
object.value = "3"

print("At end")

This just prints "At end"—none of the KVO notifications actually fire.