新建iOS single view application 名字为whatNumber,打开main storyboard选中view controoler,右上角,attribute inspector中simulated metrics 的size 选择iphone 4.7-inch这样view controller更像是一个iphone..

然后拖动三个控件到界面上lable,text field,button

最后打开assistant editor,ctrl 拖动这三个控件到viewController.swift中,会自动生成如下代码

@IBOutlet weak var resultLabel: UILabel!
@IBOutlet weak var guessField: UITextField!
@IBAction func checkBtnPressed(sender: UIButton) {

完整的代码如下:

//
//  ViewController.swift
//  whatNumber
//
//  Created by cyper on 6/2/16.
//  Copyright © 2016 Moaz Tech. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    
    let randomNum = arc4random_uniform(5)

    @IBOutlet weak var resultLabel: UILabel!
    
    @IBOutlet weak var guessField: UITextField!
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view,typically from a nib.
        
        print(randomNum)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    @IBAction func checkBtnPressed(sender: UIButton) {
        let userEntered = guessField.text
        let generated = String(randomNum)
        
        guessField.text = ""
        
        if userEntered == generated {
            resultLabel.text = "Correct Answer"
            resultLabel.textColor = UIColor.greenColor()
        } else {
            
            resultLabel.text = "Incorrect! Try Again."
            resultLabel.textColor = UIColor.redColor()
        }
        
    }
}

学到的:

在Attribute inspector中可以设置text field的Keyboard type为Number Pad,这样当text field获得焦点时弹出的就是数字键盘.

设置文本的颜色:resultLabel.textColor = UIColor.redColor()

生成随机数用func arc4random_uniform(_: UInt32) -> UInt32,比如arc4random_uniform(5)可以生成0~4的随机数字,依此类推.