Learning Swfit: Calculator App, part 2. Case, Auto Layout, Variable types

This is part 2 of my Learning Swift Calculator App.

Progress:

  • +, -, x operations are now functional
  • decimals also work

Lessons learned:

  • It’s easy to get caught up on a new programming language and forget to use universal concepts of programming that would have made my life a lot easier
    • In my haste (and learning/programming style), I jumped in with both feet, and soon I had one too many else if statements.  I cleaned up the initial logic to use case statements instead.  Not different than any other programming language out there – just common sense and cleaner programming all around.
  • Layout issues – for the first few versions, I will stick with programming for a target device (iPhone5) instead of universal design.  This can be enabled on the view controller file inspector > disable “Use Auto Layout” (thanks Dr. Hooper for pointing me to this setting!)
  • Calculators are very complicated!
    • My initial versions will ignore order of operations
    • Will not check user input for errors (for example, if the user presses + +, it will give unexpected results)
  • I have some issues with decimals (1+1.1=2.0999….) – need to check into how my values are being saved.  Again variable types seem to be haunting me.
  • Break points are super easy to use!  (Apple+”\” to add/delete)  The debug interface is intuitive and clearly shows all the variables.  The debug navigator (6th icon on the 2nd row of icons on the top left… looks like a line, 3 columns, and a line) is also a great snapshot into what’s going on – shows cpu/memory/disk/network usage.

Code as of this writing for ViewController.swift:

//
//  ViewController.swift
//  Calculator
//
//  Created by Jin S. An on 10/1/14.
//  Copyright (c) 2014 jinsungpsu.com. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    
    
    var displayString = ""
    
    @IBOutlet var calcDisplay: UITextField!

    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.
    }
    
    func updateCalculatorDisplay(buttonPressed: String) {

        switch (buttonPressed) {
        case ".","1","2","3","4","5","6","7","8","9","0":
            displayString += buttonPressed
        case "-","+","x":
            displayString += " " + buttonPressed + " "
        default:
            displayString += buttonPressed
        }
        calcDisplay.text = displayString
    }

    @IBAction func calc01(sender: AnyObject) {
        updateCalculatorDisplay("1")
    }
    @IBAction func calc02(sender: AnyObject) {
        updateCalculatorDisplay("2")
    }
    @IBAction func calc03(sender: AnyObject) {
        updateCalculatorDisplay("3")
    }
    @IBAction func calc04(sender: AnyObject) {
        updateCalculatorDisplay("4")
    }
    @IBAction func calc05(sender: AnyObject) {
        updateCalculatorDisplay("5")
    }
    @IBAction func calc06(sender: AnyObject) {
        updateCalculatorDisplay("6")
    }
    @IBAction func calc07(sender: AnyObject) {
        updateCalculatorDisplay("7")
    }
    @IBAction func calc08(sender: AnyObject) {
        updateCalculatorDisplay("8")
    }
    @IBAction func calc09(sender: AnyObject) {
        updateCalculatorDisplay("9")
    }
    @IBAction func calcDecimal(sender: AnyObject) {
        updateCalculatorDisplay(".")
    }
    @IBAction func calc00(sender: AnyObject) {
        updateCalculatorDisplay("0")
    }
    @IBAction func calcPlus(sender: AnyObject) {
        updateCalculatorDisplay("+")
    }
    @IBAction func calcMinus(sender: AnyObject) {
        updateCalculatorDisplay("-")
    }
    @IBAction func calcMultiply(sender: AnyObject) {
        updateCalculatorDisplay("x")
   }
    @IBAction func calcEqual(sender: AnyObject) {
        var tempArray = displayString.componentsSeparatedByString(" ")
        var currentOperation = "initial"
        var calculatedValue:Float = 0.0;
        for tempValue in tempArray {
            switch (tempValue) {
                case "+":
                    currentOperation = "+"
                case "-":
                    currentOperation = "-"
                case "x":
                    currentOperation = "x"
                case "%":
                    currentOperation = "%"
                default:
                    switch (currentOperation) {
                        case "+":
                            calculatedValue += (tempValue as NSString).floatValue
                        case "-":
                            calculatedValue -= (tempValue as NSString).floatValue
                        case "x":
                            calculatedValue *= (tempValue as NSString).floatValue
                       case "initial":
                            calculatedValue = (tempValue as NSString).floatValue
                        default:
                            calculatedValue += 0.0
                    }
            }
        }
        displayString = "=" + calculatedValue.description
        calcDisplay.text = displayString
    }
    @IBAction func calcClear(sender: AnyObject) {
        displayString = ""
        calcDisplay.text = ""
    }
}


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