[iOS]网络编程专题:使用NSConnection下载数据

使用NSConnection下载数据

1.创建NSConnection对象，设置委托对象

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[self urlString]]];

[NSURLConnection connectionWithRequest:request delegate:self];

2. NSURLConnection delegate委托方法

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;

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

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;

- (void)connectionDidFinishLoading:(NSURLConnection *)connection;

3. 实现委托方法

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

// store data

[self.receivedData setLength:0]; //通常在这里先清空接受数据的缓存

}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {

[self.receivedData appendData:data]; //可能多次收到数据，把新的数据添加在现有数据最后

}

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

// 错误处理

}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

// disconnect

[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;

NSString *returnString = [[NSString alloc] initWithData:self.receivedData encoding:NSUTF8StringEncoding];

NSLog(returnString);

[self urlLoaded:[self urlString] data:self.receivedData];

firstTimeDownloaded = YES;

}