iPhone 开发有多难 [关闭]

iPhone 开发有多难？

swift
import UIKit
class CalculatorViewController: UIViewController {
    @IBOutlet weak var displayLabel: UILabel!
    
    var firstOperand: Double = 0
    var secondOperand: Double = 0
    var operation: String = ""
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    @IBAction func numberButtonPressed(_ sender: UIButton) {
        if let number = sender.currentTitle {
            displayLabel.text = displayLabel.text! + number
        }
    }
    
    @IBAction func operationButtonPressed(_ sender: UIButton) {
        if let op = sender.currentTitle {
            operation = op
            firstOperand = Double(displayLabel.text!)!
            displayLabel.text = ""
        }
    }
    
    @IBAction func equalsButtonPressed(_ sender: UIButton) {
        secondOperand = Double(displayLabel.text!)!
        
        switch operation {
        case "+":
            displayLabel.text = String(firstOperand + secondOperand)
        case "-":
            displayLabel.text = String(firstOperand - secondOperand)
        case "*":
            displayLabel.text = String(firstOperand * secondOperand)
        case "/":
            displayLabel.text = String(firstOperand / secondOperand)
        default:
            break
        }
    }
    
    @IBAction func clearButtonPressed(_ sender: UIButton) {
        displayLabel.text = ""
        firstOperand = 0
        secondOperand = 0
        operation = ""
    }
}