Calculator Homework Swift

//
//  ViewController.swift
//  Calculator
//
//  Created by Matan Dahan on 24/01/2018.
//  Copyright © 2018 Matan Dahan. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var resultLabel: UILabel!

    var currentString : String = ""
    var nextNumber : String = ""
    var firstNum : Double = 0
    var firstNumInteger : Int = 0
    var secondNum : Double = 0
    var secondNumInteger : Int = 0
    var counter : Int = 0
    var checkAction : Check = Check.addtion
    var lastKnownAction : Check = Check.addtion
    var result : Double = 0
    var resultInteger : Int = 0
    var isDecimal : Bool = true
    var checkNumber : Double = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        restartCalculator()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    @IBAction func buttonPressed(_ sender: UIButton) {
        if sender.tag <= 11 {
            currentString.append(sender.currentTitle!)
            updateUI(currentNeededString: currentString)
        } else if sender.tag == 19 {
            restartCalculator()
        } else {
            if firstNum == 0 && !currentString.isEmpty {
                firstNum = Double(currentString)!
                checkNumber = Double(currentString)!
                isDecimal = checkIfDecimal(number: checkNumber)
                if !isDecimal {
                    firstNumInteger = Int(currentString)!
                    updateUI(currentNeededString: "\(firstNumInteger)")
                } else {
                    updateUI(currentNeededString: "\(firstNum)")
                }
                currentString = ""
                print("First Num: \(firstNum)")
            } else if firstNum != 0 && !currentString.isEmpty {
                secondNum = Double(currentString)!
                checkNumber = Double(currentString)!
                isDecimal = checkIfDecimal(number: checkNumber)
                if !isDecimal {
                    secondNumInteger = Int(currentString)!
                    updateUI(currentNeededString: "\(secondNumInteger)")
                } else {
                    updateUI(currentNeededString: "\(secondNum)")
                }
                currentString = ""
                print("Second Num: \(secondNum)")
                whichCalculationWouldBePerformed()
            }
            if sender.tag == 12 {
                checkAction = lastKnownAction
            } else if sender.tag == 13 {
                checkAction = .addtion
            } else if sender.tag == 14 {
                checkAction = .subtraction
            } else if sender.tag == 15 {
                checkAction = . multiplication
            } else if sender.tag == 16 {
                checkAction = .division
            }
            lastKnownAction = checkAction
        }
    }

    func whichCalculationWouldBePerformed() {
        switch checkAction {
        case .addtion:
            performCalculation(calculationActionToPerform: .addtion)
        case .subtraction:
            performCalculation(calculationActionToPerform: .subtraction)
        case .equals:
            performCalculation(calculationActionToPerform: checkAction)
        case .multiplication:
            performCalculation(calculationActionToPerform: .multiplication)
        case .division:
            performCalculation(calculationActionToPerform: .division)
        }
    }

    func performCalculation(calculationActionToPerform _action : Check) {
        if _action == .addtion {
            result = firstNum + secondNum
        } else if _action == .subtraction {
            result = firstNum - secondNum
        } else if _action == .division {
            result = firstNum / secondNum
        } else if _action == .multiplication {
            result = firstNum * secondNum
        }
        firstNum = result
        checkNumber = result
        checkNumber = result
        isDecimal = checkIfDecimal(number: checkNumber)
        if !isDecimal {
            resultInteger = Int(result)
            updateUI(currentNeededString: "\(resultInteger)")
        } else {
            updateUI(currentNeededString: "\(result)")
        }
    }

    func checkIfDecimal(number : Double) -> Bool {
        if number - floor(number) > 0.000001 {
            return true
        } else {
            return false
        }
    }

    func restartCalculator() {
        updateUI(currentNeededString: "0")
        firstNum = 0
        secondNum = 0
    }

    func updateUI(currentNeededString : String) {
        resultLabel.text = currentNeededString
    }
}

enum Check {
    case addtion
    case subtraction
    case multiplication
    case division
    case equals
}