Xcode

IDE(Integrated Development Environment)集成开发环境

ViewController.swift

import Cocoaclass ViewController: NSViewController {	//"!"为隐式封拆的可选类型，相当于告诉编译器，在该变量为nil时绝不会访问它	@IBOutlet weak var loanAmountField :NSTextField!	@IBOutlet weak var interestRateField : NSTextField!	@IBOutlet weak var yearsField : NSTextField!	@IBOutlet weak var resultsField : NSTextField!	var simpleInterestCalculator : SimpInterest = SimpInterest()		override func viewDidLoad() {		super.viewDidLoad()		// Do any additional setup after loading the view.	}	override var representedObject: Any? {		didSet {		// Update the view, if already loaded.		}	}	[@IBAction](https://my.oschina.net/u/866341) func buttonClicked(sender : NSButton){		var result : Double		result = simpleInterestCalculator.calculate(loanAmount: loanAmountField.doubleValue, interestRate: interestRateField.doubleValue , years: yearsField.integerValue)		self.resultsField.stringValue = result.description//description让类能够返回其数据的String表示			}}

SimpInterest.swift

import Foundationclass SimpInterest{	func calculate(loanAmount : Double ,interestRate :Double,years : Int) -> Double{		let interestRate1 = loanAmount / 100.0		let interest = Double(years) * interestRate1 * interestRate//单利计算		return interestRate + interest		}}