Swift轻松入门——基本语法介绍和详细地Demo讲解（利用WebView打开百度、新浪等网页）

定义常量用let关键字 let country = "China"，定义变量用var关键字var team = "HiLink",注意:Swift与Objective-C的区别——定义字符串不需要加"@",常量、变量的类型是可选的，如果在声明的同时就赋值的话，编译器会自己推断出变量类型，比如county和team就是字符串类型，再比如说定义var pi = 3，那么pi就是int类型，那我想让pi变为float类型该怎么办呢？我们只需在声明的时候显示地制定类型就可以了，比如var pi:Float = 3,此时pi就是float类型了

1 数组、字典用[]来定义，可以用下标或键(key)来访问，比如var animals = ["dog","cat","moneky"]定义一个动物数组，再比如var webSites = ["baidu":"www.baidu.com","sina":"www.sina.com"]定义一个网址字典，用webSites["baidu"]来获取“baidu”的value，即webSites["baidu"] =＝ “www.baidu.com”
2 ,如果要创建空的数组或者字典，就需要使用初始化语法，比如var animals = [String]()
3 var webSites = [Dictionary].self

Swift在控制流语法中最大的特色是：包裹条件和循环变量括号可以省略，但内容体的大括号是必须的。比如:
var salarys = [5000,10000,15000,20000]
for salary in salarys
{
    if salary > 15000
    {
        println("有钱淫～")
    }
    else
    {
        println("穷屌丝～")
    }
}
可以看到if的条件部分可以不用(),另外if的条件语句必须是Bool类型，如果把上述例子改为:
if salary
{
    println("有钱淫～")
}
则编译器会提示错误，注：println类似Objective-C的NSLog()。
再讲一下Switch语句，Swift中的Switch语句支持任意类型的数据——不仅仅是整数哦，另外switch中每个case不需要在末尾加break，只要执行了一个case后自动跳出，不会依次往下执行，例子代码如下：
let today = "Friday"
switch today
{
    case "Monday":
        println("fuck day!")
    case "Friday":
        println("nice day!")
    default:
        println("fighting day!")
}
while循环没什么特殊的就不赘述了～

swift用func来定义函数，函数原型为：func 函数名(参数1，参数2...) －> 返回类型，示例代码如下：
func whoami() -> String
{
    return "***"
}
函数原型：func 函数名(参数1，参数2...) －> 返回类型
func join(s1: String, s2: String, joiner: String) -> String 
{    return s1 + joiner + s2
}
join("hello", "world", ", ")
// returns "hello, world "


外部参数名
func join(string s1: String, toString s2: String, withJoiner joiner: String) -> String {    return s1 + joiner + s2
}
join(string: "hello", toString: "world", withJoiner: ", ")
// returns "hello, world“


Shorthand 外部参数名
func join(#string: String, #toString: String, #withJoiner : String) -> String 
{   
     return string + toString + withJoiner 
}
join(string: "hello", toString: "world", withJoiner: ", ")

默认参数值
func join(string s1: String, toString s2: String,withJoiner joiner: String = " ") -> String 
{        
    return s1 + joiner + s2
}
join(string: "hello", toString: "world", withJoiner: "-")
// returns "hello-world "
join(string: "hello", toString: "world")
// returns "hello world "

元组：把多个值组合成一个简单的复合值
let http200Status = (statusCode: 200, description: "OK")
// http200Status is of type (Int, String), and equals (200, "OK")
println("The status code is \(http200Status.statusCode)")
// prints "The status code is 200 "
println("The status message is \(http200Status.description)")
// prints "The status message is OK"  

swift中类用class来定义，类中的变量和方法与普通的变量与函数定义一致，没什么区别，对象就用类名＋构造方法生成，例子代码如下：
类定义
class ClassName{}
class Car
{
     var name:String
     init(name:String)
     {
          self.name = name
    }
    func carName() ->String
    {
          return name
     }
}
var domesticCar = Car(name: "BYD")
println(domesticCar.carName())
//prints:"BYD”

Designated&Convenience
init(parameters) 
{    
    statements
}
convenience init(parameters) 
{   
    statements
}

Stored Properties & Computed Properties
class Car
{     var name:String    
      var carName:String{        
      get{  return name; }        
      set(newName){   name = newName  }    
     }    
     init(name:String)    
    {        
           self.name = name    
     }
}
var domesticCar = Car(name: "BYD")
var name = domesticCar.carName
domesticCar.carName = "BMW "

1 swift中如果在声明一个变量时不手动初始化，swift不会为该变量自动赋一个默认值，但对于Optinal的变量则不同，Optinal类型的变量如果没初始化，则swift自动会为该变量赋为nil。那怎么声明一个Optional变量呢？只要在声明时在类型后面加上? 或者!就行了，比如
2 var urlRequest:NSURLRequest? //urlRequest == nil
3 而?和!的区别就是：?表示该变量可能为nil也可能不为nil，而!则表示该变量肯定不为nil。
4 另外as表示类型转换，比如
5 webAddress = item.objectForKey(webName[0]) as! String
6 表示把value强制转换为String类型。

 1 //
 2 //  ViewController.swift
 3 //  XSurfing
 4 //
 5 //  Created by huixinming on 6/24/15.
 6 //  Copyright (c) 2015 huixinming. All rights reserved.
 7 //
 8 
 9 //引入相关头文件
10 import UIKit
11 import Foundation
12 
13 class ViewController: UITableViewController {
14     //创建相关网站字典模型
15     let baidu = ["百度":"http://www.baidu.com"]
16     let sina = ["新浪":"http://sina.com"]
17     let phoenix = ["凤凰网":"http://www.ifeng.com"]
18     //用于存储需要显示的网站
19     var webSites:NSMutableArray
20     //选择的网址，默认是百度
21     var webAddress:String = "http://www.baidu.com"
22     //storyboard创建controller必须要实现的初始化方法，可以在此处给成员变量赋初值
23     required init!(coder aDecoder: NSCoder!) {
24         //把要显示的网站添加进来，有个疑问是：在该方法中super.init方法必须在初始化完子类的成员变量后才能调用
25         webSites = [baidu,sina,phoenix]
26         super.init(coder: aDecoder)
27     }
28     //覆盖父类的相关方法
29     override func viewDidLoad() {
30         super.viewDidLoad()
31         // Do any additional setup after loading the view, typically from a nib.
32         //设置该ViewController的title和根View的背景色
33         self.navigationItem.title = "XSuring"
34         self.view.backgroundColor = UIColor.redColor()
35     }
36     override func didReceiveMemoryWarning() {
37         super.didReceiveMemoryWarning()
38         // Dispose of any resources that can be recreated.
39     }
40     //覆盖UITableView的相关delegate方法
41     override func numberOfSectionsInTableView(tableView: UITableView) -> Int
42     {
43         return 1
44     }
45     override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
46     {
47         //返回要显示的行数
48         return webSites.count
49     }
50     override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
51     {
52         //设置cell的相关显示
53         let cellIdentifier:String = "webCell"
54         var cell:UITableViewCell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier) as! UITableViewCell
55         var row = indexPath.row
56         var item = webSites[row] as! NSDictionary
57         var webName:NSArray = item.allKeys
58         cell.textLabel?.text = webName[0] as? String
59         return cell
60     }
61     override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath)
62     {
63         var row = indexPath.row
64         var item = webSites[row] as! NSDictionary
65         var webName:NSArray = item.allKeys as NSArray
66         webAddress = item.objectForKey(webName[0]) as! String
67         //点击时跳转到“网页内容显示界面，showDetailWebContent是storyboard segue identifier”
68         self.performSegueWithIdentifier("showDetailWebContent", sender: self)
69     }
70     //把选中的网站url传递给“网页内容显示controller”
71     override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?)
72     {
73         var webViewCOntroller= segue.destinationViewController as! WebViewController
74         webViewController.detailURL = webAddress
75     }
76 }

 1 //
 2 //  WebViewController.swift
 3 //  XSurfing
 4 //
 5 //  Created by huixinming on 6/26/15.
 6 //  Copyright (c) 2015 huixinming. All rights reserved.
 7 //
 8 import UIKit
 9 import Foundation
10 
11 class WebViewController: UIViewController,UIWebViewDelegate {
12     @IBOutlet weak var webView: UIWebView!
13     var tipLabel:UILabel
14     var loading:UIActivityIndicatorView
15     //需要加在的url，默认是百度
16     var detailURL:String = "http//www.baidu.com"
17     var urlRequest:NSURLRequest?
18     required init(coder aDecoder: NSCoder) {
19         //初始化提示语和加载框
20         tipLabel = UILabel(frame: CGRectMake(20, 100, 400, 200))
21         loading = UIActivityIndicatorView(activityIndicatorStyle:.Gray)
22         super.init(coder: aDecoder)
23     }
24     override func viewDidLoad() {
25         super.viewDidLoad()
26         //构建url请求对象
27         var url = NSURL(string: detailURL)
28         urlRequest = NSURLRequest(URL: url!)
29         webView.loadRequest(urlRequest!)
30         //把webview的委托设为自己
31         webView.delegate = self
32         tipLabel.backgroundColor = UIColor.clearColor()
33         tipLabel.numberOfLines = 0
34         webView.scrollView.addSubview(loading)
35         loading.center = webView.center
36     }
37     func webViewDidStartLoad(webView: UIWebView)
38     {
39         //开始加载网页时显示loading框
40         loading.startAnimating()
41     }
42     func webViewDidFinishLoad(webView: UIWebView)
43     {
44         //当网页加载完成后，消失loading框和提示语
45         loading.stopAnimating()
46         tipLabel.removeFromSuperview()
47     }
48     func webView(webView: UIWebView, didFailLoadWithError error: NSError)
49     {
50         //当网页加载失败时，消失loading框，显示提示语
51         loading.stopAnimating()
52         tipLabel.text = "ERROR!"
53         view.addSubview(tipLabel)
54     }
55 }