确认网络环境

网络编程 开发web等网络应用程序的时候，需要确认网络环境，连接情况等信息。如果没有处理它们，是不会通过apple的审查的。 系统自带的网络检查是原生的，AFNetworking也为我们添加了相关检测机制，所以这个直接在介绍AFNetworking的时候详解吧。
使用

NSURLConnection

下载数据

1. 创建对象
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]];
[NSURLConnection connectionWithRequest:request delegate:self];

2. NSURLConnection delegate 委托方法
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

}

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

}

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

}

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

}

3. 实现委托方法
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
self.receiveData.length = 0;//先清空数据
}

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

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
//错误处理
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
NSString *returnString = [[NSString alloc]initWithData:self.receiveData encoding:NSUTF8StringEncoding];
firstTimeDownloaded = YES;
}