CounterModel

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

import UIKit

var str = "Hello, playground"

class Counter:NSObject, NSCopying{
    var count = 0;
    
    func add(){
        count++
    }
    
    func sub(){
        if (count > 0){
            count--
        }
    }
    
    func reset(){
        count = 0
    }
    
    // NSCopying
    func copyWithZone(zone: NSZone) -> AnyObject! {
        var newInstance = Counter()
        newInstance.count = self.count
        return newInstance}
}


let counter = Counter()
counter.add()
counter.sub()
counter.sub()
counter.add()
counter.add()
counter.reset()