Object-c / iOS：如何使用asynchronous从URL获取数据？

我的朋友看到​​我的代码，一部分是从URL获取plist数据

他告诉我不要使用同步，使用asynchronous

但我不知道如何以简单的方式做asynchronous

这是我在程序中使用的代码

NSURL *theURL = [[NSURL alloc]initWithString:@"http://someurllink.php" ]; NSURLRequest *theRequest=[NSURLRequest requestWithURL:theURL cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0]; NSData *returnData = [NSURLConnection sendSynchronousRequest:theRequest returningResponse:nil error:nil]; NSString *listFile = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding]; self.plist = [listFile propertyList]; [self.tableView reloadData]; [listFile autorelease]; 

如何更改我的代码使用asynchronous获取数据？

非常感谢所有答复和答案：）

Answer 1

简答 ：您可以使用

 + (NSURLConnection *)connectionWithRequest:(NSURLRequest *)request delegate:(id)delegate; 

有关非正式委托协议，请参阅NSURLConnectionDelegate（所有方法都是可选的）

很长的回答 ：

asynchronous下载数据并不像同步方法那么简单。 首先，您必须创build自己的数据容器，例如文件容器

 //under documents folder/temp.xml file = [[SomeUtils getDocumentsDirectory] stringByAppendingPathComponent:@"temp.xml"] NSFileManager *fileManager = [NSFileManager defaultManager]; if(![fileManager fileExistsAtPath:file]) { [fileManager createFileAtPath:file contents:nil attributes:nil]; } 

当您连接到服务器时：

 [NSURLConnection connectionWithRequest:myRequest delegate:self]; 

您必须使用asynchronous接收的数据填充容器：

 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:file]; [fileHandle seekToEndOfFile]; [fileHandle writeData:data]; [fileHandle closeFile]; } 

您必须使用以下方式pipe理遇到的错误

 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 

如果你想捕获服务器响应：

 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response 

连接完成加载时处理：

 - (void)connectionDidFinishLoading:(NSURLConnection *)connection 

Answer 2

对于HTML源代码的asynchronous获取，我build议你使用AFNetworking

1）然后子类AFHTTPCLient，例如：

 //WebClientHelper.h #import "AFHTTPClient.h" @interface WebClientHelper : AFHTTPClient{ } +(WebClientHelper *)sharedClient; @end //WebClientHelper.m #import "WebClientHelper.h" #import "AFHTTPRequestOperation.h" NSString *const gWebBaseURL = @"http://dummyBaseURL.com/"; @implementation WebClientHelper +(WebClientHelper *)sharedClient { static WebClientHelper * _sharedClient = nil; static dispatch_once_t oncePredicate; dispatch_once(&oncePredicate, ^{ _sharedClient = [[self alloc] initWithBaseURL:[NSURL URLWithString:gWebBaseURL]]; }); return _sharedClient; } - (id)initWithBaseURL:(NSURL *)url { self = [super initWithBaseURL:url]; if (!self) { return nil; } [self registerHTTPOperationClass:[AFHTTPRequestOperation class]]; return self; } @end 

2）请求asynchronousHTML源代码，把这个代码放在任何相关的部分

 NSString *testNewsURL = @"http://whatever.com"; NSURL *url = [NSURL URLWithString:testNewsURL]; NSURLRequest *request = [NSURLRequest requestWithURL:url]; AFHTTPRequestOperation *operationHttp = [[WebClientHelper sharedClient] HTTPRequestOperationWithRequest:request success:^(AFHTTPRequestOperation *operation, id responseObject) { NSString *szResponse = [[[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding] autorelease]; NSLog(@"Response: %@", szResponse ); } failure:^(AFHTTPRequestOperation *operation, NSError *error) { NSLog(@"Operation Error: %@", error.localizedDescription); }]; [[WebClientHelper sharedClient] enqueueHTTPRequestOperation:operationHttp];