CODEWITHSUNDEEP
swift
Ricardo
Ricardo

Reputation: 708

Swift 2.0 operators

Why I can do this:

number *= operand
number += operand

but not this (not getting the right result):

number /= operand
number -= operand

8 - 3 gives me -5 and 8 / 2 gives me 0. If I do

number = operand / displayValue
number = operand - displayValue

I get the right answer.

I'm new to swift and iOS development in general. Thanks for your answer!

This is the actual code from the simple calculator:

class ViewController: UIViewController {

    @IBOutlet weak var label: UILabel!

    var isFirstDigit = true
    var operand1: Double = 0
    var operation = "="

    var displayValue: Double {

        get {
            return NSNumberFormatter().numberFromString(label.text!)!.doubleValue
        }

        set {
            label.text = String(format: "%.0f ", newValue)
            isFirstDigit = true
            operation = "="
        }
    }

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

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


    @IBAction func digit(sender: UIButton) {
        let digit = sender.currentTitle!
        label.text = isFirstDigit ? digit : label.text! + digit
        isFirstDigit = false
    }

    @IBAction func cancel(sender: AnyObject) {
         displayValue = 0
    }

    @IBAction func calculate(sender: UIButton) {
        switch operation {
            case "/": displayValue /= operand1
            case "*": displayValue *= operand1
            case "+": displayValue += operand1
            case "-": displayValue -= operand1
            default: break
        }
    }

    @IBAction func operations(sender: UIButton) {
        operation = sender.currentTitle!
        operand1  = displayValue
        isFirstDigit = true
    }
}

Upvotes: 2

Views: 83

Answers (1)

Lucas
Lucas

Reputation: 278

I have tried this on Playground and it seems to be working just fine.

enter image description here

EDIT:

I have checked your code on XCode and was able to fix the issue by changing this: 

// Runs the operations.
switch operation {

    case "/": operand1 /= displayValue
    case "*": operand1 *= displayValue
    case "+": operand1 += displayValue
    case "-": operand1 -= displayValue

    default: break
    }

    // Updates the text on the Label.
    label.text = "\(operand1)"

It seems like you were executing the operations in the inverse order, which explains why "+" and "*" were working properly but not "/" and "-".

Upvotes: 3

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