如何使用NSUrlConnection從Web獲取數據？

Question

在我的應用程序中，我想使用NSURLConnection類。那麼請告訴我如何使用這個？這包含了很多委託方法，請告訴我如何使用它們？

Answer 1

啓動使用

self.responseData = [NSMutableData data]; 
NSURL *url = [NSURL URLWithString:@"http://sampleurl/"]; 
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 
connection = [[NSURLConnection alloc] initWithRequest:request delegate:self]; 
[connection autorelease]; 

連接，您可以看看在connectionDidFinishLoading委託方法

#pragma mark - NSURLConnection Delegate Methods 

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { 
    [self.responseData setLength:0]; 
} 

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { 
    [self.responseData appendData:data]; 
} 

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { 
    NSLog(@"Connection failed: %@", [error description]); 
} 

- (void)connectionDidFinishLoading:(NSURLConnection *)connection { 
     //Getting your response string 
    NSString *responseString = [[NSString alloc] initWithData:self.responseData encoding:NSUTF8StringEncoding]; 
self.responseData = nil; 
    } 

響應爲了您的內存泄漏問題

聲明在接口文件

響應數據

NSMutableData *_responseData; 

財產如下

@property (nonatomic, retain) NSMutableData *responseData; 

和合成它

@synthesize responseData = _responseData; 

不要釋放它的任何地方（我們使用便捷的構造函數分配）。我們已經在connectionDidFinishLoading方法中將它設置爲nil。

Answer 2

在iOS 5中和OS X 10.7或更高版本，可以異步使用加載數據如下：

NSURL *url = [NSURL URLWithString:@"http://sampleurl/"]; 
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 

[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue currentQueue] 
     completionHandler: ^(NSURLResponse * response, NSData * data, NSError * error) { 
      NSHTTPURLResponse * httpResponse = (NSHTTPURLResponse*)response; 
      if(httpResponse.statusCode == 200) { 
       //your code to handle the data 
      } 
     } 
]; 

或者，如果你想同步做到這一點（不推薦，如果要加載大量的數據，因爲它會掛應用程序）（在OS X 10.2+和iOS 2.0+提供）

NSURL *url = [NSURL URLWithString:@"http://sampleurl/"]; 
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 
NSURLResponse * response; 
NSError * error; 
NSData * data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];