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iOS NSURLConnection和异步网络请求

时间:2014-05-09 12:37:08      阅读:550      评论:0      收藏:0      [点我收藏+]

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在日常应用中,我们往往使用AFNetworking等第三方库来实现网络请求部分。这篇文章会简要地介绍一下如何使用NSURLConnection来进行异步的网络请求。

我们先看一个小demo

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- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    NSString *urlStr = @"http://www.baidu.com";
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlStr]];
    
    //从这个试验可以看出,connection的函数在 mainrunloop运行for循环时根本无法被调用,由此可见,这里的connection是在mainThread中运行的。
    NSURLConnection *con = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    
    for(int i = 0 ;i<10000;i++)
    {
        NSLog(@"%d",i);
    }
    
    NSLog(@"for end==========");
}



- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    NSLog(@"good!!!!!!!!");
}
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看下输入

2014-05-05 10:34:18.861 UrlConnectionASyncTest[9988:60b] 9997
2014-05-05 10:34:18.862 UrlConnectionASyncTest[9988:60b] 9998
2014-05-05 10:34:18.862 UrlConnectionASyncTest[9988:60b] 9999
2014-05-05 10:34:18.862 UrlConnectionASyncTest[9988:60b] for end==========
2014-05-05 10:34:18.865 UrlConnectionASyncTest[9988:60b] good!!!!!!!!

查看苹果的文档会发现如下的解释

By default, a connection is scheduled on the current thread in the default mode when it is created. If you create a connection with the initWithRequest:delegate:startImmediately: method and provide NO for the startImmediately parameter, you can instead schedule the connection on an operation queue before starting it with the start method.

You cannot reschedule a connection after it has started.

这就是说,如果你仅仅通过在主线程中使用initWithRequest:delegate:方法创建一个connection对象,它会默认地加入到mainThread中,这样当数据返回时,会在main thread中执行,这就会影响UI的刷新。这种connnection不是同步的connection,因为它在没有得到数据时就可以继续执行其他代码,但也不是那种真正的异步connection,因为它的回调函数会在main thread中执行,会影响main thread中的其他函数执行。

那么如何创建一个在其他thread中执行回调函数的connection呢?系统提供了2套方法,

第一套是使用类方法,sendAsynchronousRequest:queue:completionHandler:

第二套是使用几个对象方法,顺序如下

1.使用initWithRequest:delegate:startImmediately:生成一个不立即开始的connnection

2.通过scheduleInRunLoop:forMode: 或者 setDelegateQueue: 设置回调方法运行的thread,推荐使用第二个。

3.调用start开始connection请求。

下面给出一个demo

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- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    NSString *urlStr = @"http://www.baidu.com";
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlStr]];

    //从这个试验可以看出,connection的函数在 mainrunloop运行for循环时根本无法被调用,由此可见,这里的connection是在mainThread中运行的。
    // NSURLConnection *con = [[NSURLConnection alloc] initWithRequest:request delegate:self];

    NSURLConnection *con = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];

    [con setDelegateQueue:[[NSOperationQueue alloc] init]];
    [con start];
    
    for(int i = 0 ;i<10000;i++)
    {
        NSLog(@"%d",i);
    }
    
    NSLog(@"for end==========");
}



- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
  //  NSLog(@"data is %@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
    NSLog(@"good!!!!!!!!");
}
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结果如下

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2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 344
2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 345
2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 346
2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 347
2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 348
2014-05-05 11:23:15.129 UrlConnectionASyncTest[10147:60b] 349
2014-05-05 11:23:15.130 UrlConnectionASyncTest[10147:60b] 350
2014-05-05 11:23:15.134 UrlConnectionASyncTest[10147:4207] good!!!!!!!!
2014-05-05 11:23:15.143 UrlConnectionASyncTest[10147:60b] 351
2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:60b] 352
2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:4207] good!!!!!!!!
2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:60b] 353
2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:60b] 354
2014-05-05 11:23:15.144 UrlConnectionASyncTest[10147:60b] 355
2014-05-05 11:23:15.145 UrlConnectionASyncTest[10147:60b] 356
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可以看出connection的回调函数已经不再main thread中执行了!

 

 

iOS NSURLConnection和异步网络请求,布布扣,bubuko.com

iOS NSURLConnection和异步网络请求

标签:style   blog   class   code   java   tar   

原文地址:http://www.cnblogs.com/breezemist/p/3708808.html

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