Add a history on calculator (iOS) - ios

Question

I'm having a problem adding a history to calculator (lblHistory Label)
I want to store my previous inputs in the lblHistory : UILabel
but all it did is store the first number and its operation.
Is there any algorithm that you will store all previous inputs of your calculator?
This is my class MyCalculator.swift
Class MyCalculator
//
// MyCalculator.swift
// Calculator
//
// Created by
// abcdefgh
//
import Foundation
class MyCalculator
{
var memory: Float = 0
var percentnum: Float = 0
var currentNum: Float = 0
var result: Float = 0
var operation: String = ""
var isOperation: Bool = false
var isRepeatOperation: Bool = false
var isNum: Bool = false
func operation (operation:String) -> Float
{
if operation == "+" {
result = result + currentNum
}
else if operation == "-" {
result = result - currentNum
}
else if operation == "*" {
result = result * currentNum
}
else if operation == "/" {
result = result / currentNum
}
return result
}
func percent(percentNum:Float) ->Float
{
let valpercent = percentNum * 0.01
result = result * valpercent
return result
}
func clearAll() {
result = 0
currentNum = 0
isNum = false
}
}
and this is the view controller of my calculator.
View Controller
/ ViewController.swift
// Calculator
//
// Created by
// abcdefgh
//
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
//Start Calculator
//Label History: This is where the history is displayed
#IBOutlet weak var lblHistory: UILabel!
//Label Result: This is where the result is displayed
#IBOutlet weak var lblResult: UILabel!
//Initialization
let calc = MyCalculator() //call the class MyCalculator
//Function for Number Inputs
#IBAction func btnNumInput(sender: AnyObject)
{
let num = sender.currentTitle
if calc.isNum == false
{
lblResult.text = num
calc.isNum = true
}
else
{
lblResult.text = lblResult.text! + num!!
}
calc.isRepeatOperation = false
lblResult.adjustsFontSizeToFitWidth = true
}
//Function for Operations
#IBAction func btnOperations(sender: AnyObject)
{
calc.isNum = false
if calc.isOperation && !calc.isRepeatOperation
{
calc.currentNum = Float(lblResult.text!)!
if calc.operation == "+"
{
calc.result = calc.operation("+")
}
else if calc.operation == "-"
{
calc.result = calc.operation("-")
}
else if calc.operation == "*"
{
calc.result = calc.operation("*")
}
else if calc.operation == "/"
{
calc.result = calc.operation("/")
}
if calc.operation == "/" && calc.currentNum == 0
{
lblResult.text = "Cannot divide by zero"
lblResult.adjustsFontSizeToFitWidth = true
}
else
{
let stringresult = String(format:"%g" , calc.result)
lblResult.text = "\(stringresult)"
calc.isOperation = false
}
}
else
{
calc.result = Float(lblResult.text!)!
}
let strresult = String(format:"%g", calc.result)
calc.operation = sender.currentTitle!!
lblHistory.text = strresult + calc.operation
calc.isOperation = true
calc.isRepeatOperation = true
}
From this code here:
let strresult = String(format:"%g", calc.result)
calc.operation = sender.currentTitle!!
lblHistory.text = strresult + calc.operation
this should store any input from the history label but it will only store the first input and its operator.
The result:
2+2 =4 //this is the input variables and operation
//the result is 4 and display on lblResult: UILabel
2+ // the "2+" is only stored in lblHistory: UILabel not the whole input itself