swift语言IOS8开发战记24 解析Json

在IOS中使用NSURLConnection实现http通信，NSURLConnection提供了异步和同步两种通信方式，同步请求会造成进程阻塞，通常我们使用异步的方式，不管同步还是异步，建立通信的基本步骤都是一样的：

1，创建NSURL

2，创建Request对象

3，创建NSURLConnection连接

第3步结束后就建立了一个http连接。

这里我们用一个开放的api做例子：

http://www.weather.com.cn/adat/sk/101010100.html

这是北京市的当前天气信息的json，我们首先来写一个同步的网络连接来获取这个json，新建一个工程，在页面上添加一个按钮，每次点击按钮就会输出json的内容到控制台，控制器代码：

import UIKit

class ViewController: UIViewController {

    @IBAction func showWeatherJson(sender: UIButton) {
        //创建url
        var url:NSURL! = NSURL(string: "http://www.weather.com.cn/adat/sk/101010100.html")
       //创建请求对象
        var urlRequest:NSURLRequest = NSURLRequest(URL: url)
        //创建响应对象
        var response:NSURLResponse?
        //创建错误对象
        var error:NSError?
        //发出请求
        var data:NSData? = NSURLConnection.sendSynchronousRequest(urlRequest, returningResponse: &response, error: &error)
        if error != nil
        {
        println(error?.code)
        println(error?.description)
        
        } else {
        var jsonString = NSString(data: data!, encoding: NSUTF8StringEncoding)
            println(jsonString)
        
        }
        
    }
}

下面来展示异步请求的代码：

import UIKit

class ViewController: UIViewController,NSURLConnectionDataDelegate,NSURLConnectionDelegate {

   
    @IBAction func getWeatherJson(sender: UIButton) {
        
        //创建NSURL对象
        var url:NSURL! = NSURL(string: "http://www.weather.com.cn/adat/sk/101010100.html")
        //创建请求对象
        var urlRequest:NSURLRequest = NSURLRequest(URL: url)
        //网络连接对象
        var conn:NSURLConnection? = NSURLConnection(request: urlRequest, delegate: self)
        conn?.scheduleInRunLoop(NSRunLoop.currentRunLoop(), forMode: NSRunLoopCommonModes)
        //执行
        conn?.start()
        
    }
}

    func connection(connection: NSURLConnection, willSendRequest request: NSURLRequest, redirectResponse response: NSURLResponse?) -> NSURLRequest? {
        //将要发送请求
        return request
    }
    func connection(connection: NSURLConnection, didReceiveResponse response: NSURLResponse) {
        //接收响应
    }
    func connection(connection: NSURLConnection, didReceiveData data: NSData) {
        //收到数据
    }
    func connection(connection: NSURLConnection, needNewBodyStream request: NSURLRequest) -> NSInputStream? {
        //需要新的内容流
        return request.HTTPBodyStream
    }
    func connection(connection: NSURLConnection, didSendBodyData bytesWritten: Int, totalBytesWritten: Int, totalBytesExpectedToWrite: Int) {
        //发送数据请求
    }
    func connection(connection: NSURLConnection, willCacheResponse cachedResponse: NSCachedURLResponse) -> NSCachedURLResponse? {
        //缓存响应
        return cachedResponse
    }
    func connectionDidFinishLoading(connection: NSURLConnection) {
        //请求结束
    }

 var jsonData:NSMutableData = NSMutableData()
    func connection(connection: NSURLConnection, didReceiveData data: NSData) {
        //收到数据
        jsonData.appendData(data)
    }

func connectionDidFinishLoading(connection: NSURLConnection) {
        //请求结束
        var jsonString = NSString(data: jsonData, encoding: NSUTF8StringEncoding)
        println(jsonString)
    }