Swift Calculator操作員問題

Question

大家好，謝謝您訪問我的頁面。 我目前正在學習為班級創建一個計算器，但是請注意，例如，當我鍵入內容時發生錯誤：

5 + 5 = 10 //這是正確的

5 + 2 * 3 + 5 = 26 //尚無問題

5 + 2 = 7 +（將最后一個運算符與數字相加。這意味着在我選擇要添加的數字之前，屏幕將顯示9。）

我應該如何思考才能解決此問題的任何建議將不勝感激。

import UIKit
import AVFoundation

class ViewController: UIViewController {

    enum Operation: String {
        case Divide = "/"
        case Multiple = "*"
        case Subtract = "-"
        case Add = "+"
        case Empty = "Empty"
    }

    @IBOutlet weak var outputLbl: UILabel!

    // This is initialized once the app loads. 

    var btnSound: AVAudioPlayer!

    var runningNumber = ""
    var leftValStr = ""
    var rightValStr = ""
    var currentOperation: Operation = Operation.Empty
    var result = ""


    override func viewDidLoad() {
        super.viewDidLoad()

        let path = NSBundle.mainBundle().pathForResource("btn", ofType: "wav")
        let soundUrl = NSURL(fileURLWithPath: path!)

        do {
            try btnSound = AVAudioPlayer(contentsOfURL: soundUrl)
            btnSound.prepareToPlay()
        } catch let err as NSError {
            print(err.debugDescription)
        }
        // Do any additional setup after loading the view, typically from a nib.
    }

    @IBAction func numberPressed(btn: UIButton) {
        playSound()

        // Each button is assigned to a tag from 0-9. 
        // When button is pressed it is stored to btn.
        runningNumber += "\(btn.tag)"
        outputLbl.text = runningNumber
    }

    @IBAction func onDividePressed(sender: AnyObject) {
        processOperation(Operation.Divide)
    }

    @IBAction func onMultiplyPressed(sender: AnyObject) {
        processOperation(Operation.Multiple)
    }

    @IBAction func onSubtractPressed(sender: AnyObject) {
        processOperation(Operation.Subtract)
    }

    @IBAction func onAddPressed(sender: AnyObject) {
        processOperation(Operation.Add)
    }

    @IBAction func onEqualPressed(sender: AnyObject) {
        processOperation(currentOperation)
    }

    @IBAction func onClearPressed(sender: AnyObject) {
        clearCalcuator()
    }



    // op is what is storing the Operator. It could have been named anything
    func processOperation(op: Operation) {
        playSound()

        if currentOperation != Operation.Empty {
            // Run some math.

            // A user selected an operator, but then selected another
            // operator without first selecting a number
            if runningNumber != "" {
                rightValStr = runningNumber
                runningNumber = ""

            }

            if currentOperation == Operation.Multiple {
                result = "\(Double(leftValStr)! * Double(rightValStr)!)"
            } else if currentOperation == Operation.Divide {
                result = "\(Double(leftValStr)! / Double(rightValStr)!)"
            } else if currentOperation == Operation.Subtract {
                result = "\(Double(leftValStr)! - Double(rightValStr)!)"
            } else if currentOperation == Operation.Add {
                result = "\(Double(leftValStr)! + Double(rightValStr)!)"
            }

            leftValStr = result
            outputLbl.text = result

            currentOperation = op

        } else {
            // This is the first time an Operator has been pressed.

            leftValStr = runningNumber
            runningNumber = ""
            currentOperation = op
        }
    }

    func clearCalcuator() {
        playSound()

        if outputLbl.text != "0" {
            runningNumber = ""
            leftValStr = ""
            rightValStr = ""
            currentOperation = Operation.Empty

        }

        outputLbl.text = "0"
    }


    // Function was created to keep the code DRY. 
    // Now can use playSound() on top. Exp: Line 51
    func playSound() {
        if btnSound.playing {
            btnSound.stop()
        }

        btnSound.play()
    }
}

我仍然是SWIFT的初學者，但希望通過向了解得更多的人學習來改善自己。 如果您對我目前的代碼也有任何建議，以及如何改進，我們將很高興歡迎所有建議。 再次感謝你。

Answer 1

您描述的行為是以下事實的結果： =的@IBAction傳遞了currentOperation的Operation ，這意味着如果最后一個操作為+ ，則意味着=按鈕的行為將與再次單擊+ 。 這就是為什么您看到自己的行為的原因。

為了解決這個問題，您需要確保在按= ， processOperation會將currentOperation設置為其他值，以便在您下次調用processOperation ，不執行進一步的計算。 為此，您需要做的就是在= Operation增加一種case ：

enum Operation: String {
    case Divide = "/"
    case Multiple = "*"
    case Subtract = "-"
    case Add = "+"
    case Equal = "="
    case Empty = "Empty"
}

然后將@IBAction更改為=以僅通過此Operation而不是currentOperation ：

@IBAction func onEqualPressed(sender: AnyObject) {
    processOperation(.Equal)
}

因此，當您調用processOperation ，它將執行currentOperation ，然后完成時，它將currentOperation重置為Operation.Equal ，下次您下次對processOperation進行下一次調用時，它將不會基於重復任何進一步的計算.Equal 。

Answer 2

您應該將其保存到一個變量中，除非清除該變量，否則將對其進行下一步操作。

var answer = 5 + 2

在計算器中顯示您的answer變量，然后如果按下另一個操作按鈕，則使用答案變量ex + 9將是answer + 9 ，如果用戶點擊clear ，則單擊=將更新ui以顯示16 ，只需將answer = 0設置answer = 0