izmenjen kod

//
//  ViewController.swift
//  Calculator
//
//  Created by Milos on 4/3/18.
//  Copyright © 2018 Milos. All rights reserved.
//

import UIKit

enum Operation:String {
    case ADDITION = "+"
    case SUBSTRACTION = "-"
    case DIVISION = "/"
    case MULTIPLICATION = "*"
    case NULL = "Null"
}

class ViewController: UIViewController {

    @IBOutlet weak var outputLbl: UILabel!

	var val1 = ""
    var val2 = ""
    var runningNumber = ""
    var runningOpNum = ""
    var res = ""
    var currentOperation:Operation = .NULL

    override func viewDidLoad() {
        super.viewDidLoad()
         outputLbl.text = "0"
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    @IBAction func numberPressed(_ sender: RoundButton) {
        if runningNumber.count <= 8 {
            runningNumber += "\(sender.tag)"
            outputLbl.text = runningNumber
        }
    }

    @IBAction func allClearPressed(_ sender: RoundButton) {
        val1 = ""
        val2 = ""
		runningNumber = ""
        res = ""
        currentOperation = .NULL
        outputLbl.text = "0"
    }

    @IBAction func equalPressed(_ sender: RoundButton) {
        operation(operation: currentOperation)
        val1 = ""
        val2 = ""
		runningNumber = ""
        res = ""
        currentOperation = .NULL
    }

    @IBAction func addPressed(_ sender: RoundButton) {
        operation(operation: .ADDITION)
        if outputLbl.text != "0"{
            outputLbl.text = "+"
        }
    }

    @IBAction func substractPressed(_ sender: RoundButton) {
        operation(operation: .SUBSTRACTION)
        if outputLbl.text != "0"{
            outputLbl.text = "-"
        }
    }

    @IBAction func multiplyPressed(_ sender: RoundButton) {
        operation(operation: .MULTIPLICATION)
        if outputLbl.text != "0"{
            outputLbl.text = "*"
        }
    }

    @IBAction func dividePressed(_ sender: RoundButton) {
         operation(operation: .DIVISION)
        if outputLbl.text != "0"{
            outputLbl.text = "/"
        }
    }

    func operation(operation: Operation) {
        if currentOperation != .NULL {
            if runningNumber != "" {
                val2 = runningNumber
                runningNumber = ""

                switch currentOperation {
				case .ADDITION:
					res = "\(Double(val1)! + Double(val2)!)"
				case .SUBSTRACTION:
					res = "\(Double(val1)! - Double(val2)!)"
				case .MULTIPLICATION:
					res = "\(Double(val1)! * Double(val2)!)"
				case .DIVISION:
					res = "\(Double(val1)! / Double(val2)!)"
				case .NULL: break
				}
                if (Double(res)!.truncatingRemainder(dividingBy: 1) == 0) {
                    res = "\(Int(Double(res)!))"
                }
                outputLbl.text = val1 + currentOperation.rawValue + val2 + "=" + res
            }
            currentOperation = operation

        }else {
            val1 = runningNumber
            runningNumber = ""
            currentOperation = operation
        }
    }

}